http://www.bbc.co.uk/news/world-us-canada-23997249
President Obama has demonstrated reluctance to "go it alone" regarding strikes on Syria
The president is clearing his desk, going all-out to persuade for a vote that he has said is vital for America's credibility.
It is also a critical moment for American perception of itself as a power in the world. But in the details of the debate over Syria, the biggest questions and the larger picture are in danger of being lost.
In essence, it's whether the world needs a super cop. And whether the US should simply assume that role.
President Barack Obama - like UK PM David Cameron, like former US President George W Bush and former UK PM Tony Blair before them - has two main arguments for intervention in the Middle East. They overlap and intertwine, but they are distinct.
The first is national interest. Mr Obama says Syria does not pose an immediate threat to the US, but its willingness to use chemical weapons threatens its allies and bases in the region.
Less frequently his administration has suggested such weapons could fall into the hands of terrorists who could use them against America.
It is pretty obvious, the bigger the world power the more its vital interests may be harmed by something happening a long way away. If the whole Middle East is in uproar, it might not make a whole heap of difference to Paraguay or Latvia.
The argument for national interest is pretty clear. The desire to intervene for what you might call 'moral reasons', is far more murky.
Mr Obama and even more forcefully Secretary of State John Kerry have said that the world can't stand aside and witness such suffering. Particularly not when it breaches, if not international law, then international norms.
It is noticeable that it is senior politicians in the US, France and the UK who are keen on this argument of liberal interventionism. It is not just Russia that won't go along with it. China won't either.
China forcefully repeats that it wants the denuclearisation of its ally North Korea. But it is reluctant to force the issue.
But it is not just those in the communist country and the former communist empire which hold that view.
You hardly hear voices raised to demand military intervention from India or Brazil, Nigeria or Japan.
Countries on the doorstep of the various Middle East crises may want someone to do something, but look askance at the idea they might take on the task themselves.
A world policeman might have more moral authority if it wasn't one of the old imperial powers or the US, which while not technically the proud possessor of an empire, has a bigger footprint than any other country in the world.
I once put it to Tony Blair that the Iraq war might have been more credible if the call for action had come from Sweden. He made the obvious point: "Well, they couldn't do it, could they?"
Which makes me wonder about that old saying, "to a hammer, every problem is a nail". In this case, you have to wonder why the hammer was forged in the first place.
The British developed their military to defend a globe-spanning empire. The US developed its military might to intervene in Europe and then to challenge the USSR.
The absence of the original purpose has not eliminated an instinct to intervene.
Maybe the word "imperialism" makes you think of arguments "that it is all about oil" or crude land grabs.
But those Victorian imperialists really did think they were bringing civilisation and Christianity, order and the rule of law to people who couldn't climb to such dizzying heights on their own.
America's belief in its own mission is more universal and not driven by racism, but there is a similar zealous enthusiasm to remake the rest of the world in its image.
Of course, stopping the horror of chemical weapons is not the same as introducing democracy at the point of a gun.
But it raises the same question of who has the authority to make the judgment that norms have been violated, and who deals out the punishment.
The UN is meant to be the body that can order global cops into action. But the US says the Security Council is broken, because of the Russian veto.
While the Russian action does look cynical, it is a bit like a prosecutor saying the jury system doesn't work because he didn't get a conviction.
Or indeed, if David Cameron said parliament didn't work because of the "no" vote. President Obama understands how it looks to the rest of the world if the US goes it alone.
It is why he was so reluctant to take the lead over Libya, why he was so slow to develop a Syria strategy.
But he's decided now that even if no-one else (apart from France) is willing to step up to the plate, it is America's job to do so. Few at home or abroad seem to agree with him - but they don't have any other answer either.
By Bridget KendallDiplomatic correspondent, BBC News
Russia's Vladimir Putin and US President Barack Obama failed to see eye to eye over Syria during the G20 summit
Both sides have claimed victory in this G20 gladiatorial contest over Syria, but identifying who is on which team is not straightforward.
So who backed Russia and who backed the United States?
According to President Vladimir Putin, the outcome was not a 50/50 split, but a balance of opinion in Russia's favour.
He claimed that, at the G20 dinner on Syria, only four countries - France, Turkey, Canada and Saudi Arabia (plus a British prime minister rebuffed by his own parliament) - had backed America.
Whereas siding with Russia in rejecting military strikes on Syria, he says, were seven nations: China, India, Indonesia, Argentina and Brazil, as well as South Africa and Italy.
Continue reading the main story
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The statement was carefully crafted to omit the controversial crux of the American plan: punitive airstrikes on Syria, to be led by the US, quite possibly without UN backing”
Yet not all the Russian president's views on Syria were endorsed by other G20 leaders.
Who else in St Petersburg publically declared, as he did, that Syria's "so-called chemical weapons attack" was in fact "a provocation staged by rebels, in hope of winning extra backing from their foreign backers"?
In making that categorical claim, the Russian leader left little room for compromise and ended up looking, perhaps, somewhat isolated.
Shifting sands
Meanwhile, President Barack Obama also declared he had enjoyed support from a majority of G20 participants, who were "comfortable" with American claims.
- to condemn the Syrian chemical weapons attack as a grave violation of the world's rules
- to agree that the evidence pointed to Syrian government culpability
- to call for a strong international response.
Alongside the US were, unsurprisingly, the two keenest cheerleaders when it comes to taking military action, French President Francois Hollande and Britain's David Cameron.
All other signatories were also longstanding US allies from around the world: Australia and Canada; from Asia, Japan and South Korea; from the Muslim world, Turkey and Saudi Arabia; and, from Europe, Spain and Italy. The last somehow got itself included in the tally on both sides of the divide.
But, tellingly, the list of Mr Obama's supporters did not include Chancellor Angela Merkel of Germany (perhaps she thought it too risky so close to a federal election).
And the statement was carefully crafted to omit the controversial crux of the American plan: punitive airstrikes on Syria, to be led by the US, quite possibly without UN backing.
'Surrender monkey'
So it is not clear-cut who backs whom - but a muddle.
Two entrenched positions from the United States and Russia bookmark opposite ends of the spectrum, with lots of vague, shifting sands in-between.
President Hollande said he would wait for the result of a UN investigation
Even the French president - no longer castigated, as was his predecessor in the Iraq days of 2003, as a "cheese-eating surrender monkey" and now embraced as America's new best friend - has begun hedging the conditions under which France would take part in strikes
- only if they targeted Syrian military installations in order to avoid civilian casualties
- only once UN inspectors had been given time to report back
- and should the UN Security Council fail to give authorisation, then so long as a broad international coalition was gathered.
So perhaps the better question to ask when it comes to this row over Syria is: who got what they wanted from this summit, and who walked away empty-handed?
If President Putin's aim was to block US plans for building international support, then he must be feeling quite pleased with himself.
He did his job as a spoiler. And he was reinforced in his views by strong expressions of concern from other quarters.
Raising their voices to object to an American plan they fear would undermine UN authority and unleash more bloodshed through "ill-advised" military action were two powerful figures of global legal and moral authority - the UN Secretary General, and the Catholic Pontiff.
Pope Francis's intervention came
in a letter he emailed from Rome to appeal to G20 leaders not to succumb to "futile" violence.
And there is little doubt that President Obama left St Petersburg looking somewhat weakened.
Far from winning new converts to his cause, he failed to broaden the international coalition of nations prepared to back military action.
At times he sounded defensive and distracted.
And now he faces an added problem - that the lack of enthusiasm for using force without UN approval shown by some leaders around the G20 table may adversely affect the already wobbly mood of the American public, and therefore the appetite in Congress for military action in Syria.
When asked how he thought the mood at G20 might affect the chances of congressional support for his plan next week, President Obama said it could cut both ways: it might put people off, but it might also make Americans more likely to rally round their president.
Perhaps he will win the endorsement of Congress.
Perhaps, in time, the United States and its allies will build the international coalition they seek.
But it is also possible that we will look back on this G20 gathering in the months to come and say - along with the vote rejecting military action in the British parliament - that this was the moment when the appetite for international intervention for humanitarians goals faltered, and this was the turning point which showed that the rest of the world no longer wants the United States to step in as the world's policeman when other institutions fail to act - however great the crisis or grave the atrocity.
Pope Francis writes letter to President Putin of Russia ahead of G20 summit
(Vatican Radio) Pope Francis has written a letter to President Vladimir Putin of Russia as he prepares to host this year's G20 summit in St. Petersburg. Listen to Lydia O'Kane's report 
Below is the full text of the Pope's letter to President Putin.
To His Excellency
Mr Vladimir Putin
President of the Russian Federation
"In the course of this year, you have the honour and the responsibility of presiding over the Group of the twenty largest economies in the world. I am aware that the Russian Federation has participated in this group from the moment of its inception and has always had a positive role to play in the promotion of good governance of the world’s finances, which have been deeply affected by the crisis of 2008.
In today’s highly interdependent context, a global financial framework with its own just and clear rules is required in order to achieve a more equitable and fraternal world, in which it is possible to overcome hunger, ensure decent employment and housing for all, as well as essential healthcare. Your presidency of the G20 this year has committed itself to consolidating the reform of the international financial organizations and to achieving a consensus on financial standards suited to today’s circumstances. However, the world economy will only develop if it allows a dignified way of life for all human beings, from the eldest to the unborn child, not just for citizens of the G20 member states but for every inhabitant of the earth, even those in extreme social situations or in the remotest places.
From this standpoint, it is clear that, for the world’s peoples, armed conflicts are always a deliberate negation of international harmony, and create profound divisions and deep wounds which require many years to heal. Wars are a concrete refusal to pursue the great economic and social goals that the international community has set itself, as seen, for example, in the Millennium Development Goals. Unfortunately, the many armed conflicts which continue to afflict the world today present us daily with dramatic images of misery, hunger, illness and death. Without peace, there can be no form of economic development. Violence never begets peace, the necessary condition for development.
The meeting of the Heads of State and Government of the twenty most powerful economies, with two-thirds of the world’s population and ninety per cent of global GDP, does not have international security as its principal purpose. Nevertheless, the meeting will surely not forget the situation in the Middle East and particularly in Syria. It is regrettable that, from the very beginning of the conflict in Syria, one-sided interests have prevailed and in fact hindered the search for a solution that would have avoided the senseless massacre now unfolding. The leaders of the G20 cannot remain indifferent to the dramatic situation of the beloved Syrian people which has lasted far too long, and even risks bringing greater suffering to a region bitterly tested by strife and needful of peace. To the leaders present, to each and every one, I make a heartfelt appeal for them to help find ways to overcome the conflicting positions and to lay aside the futile pursuit of a military solution. Rather, let there be a renewed commitment to seek, with courage and determination, a peaceful solution through dialogue and negotiation of the parties, unanimously supported by the international community. Moreover, all governments have the moral duty to do everything possible to ensure humanitarian assistance to those suffering because of the conflict, both within and beyond the country’s borders.
Mr President, in the hope that these thoughts may be a valid spiritual contribution to your meeting, I pray for the successful outcome of the G20’s work on this occasion. I invoke an abundance of blessings upon the Summit in Saint Petersburg, upon the participants and the citizens of the member states, and upon the work and efforts of the 2013 Russian Presidency of the G20.
While requesting your prayers, I take this opportunity to assure you, Mr President, of my highest consideration."
From the Vatican, 4 September 2013
(Signed)
Francis
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