Washington DC, United States - President Barack Obama faces a defining moment when he meets Russian leader Vladimir Putin at the United Nations headquarters on Monday.
As Europe struggles with overwhelming refugee arrivals, Putin surprised the West with a quick military deployment in Syria followed by a bid for negotiations to include President Bashar al-Assad, who Obama has said must go.
Now there are rising calls for world leaders gathering in New York at the UN General Assembly to set aside differences and lay the groundwork for talks to end the brutal civil war in Syria after nearly five years.
"It depends on what Putin brings to the table," William Pomeranz, a Russia analyst at the Wilson Center in Washington, told Al Jazeera, adding he's "highly sceptical" the US and Russia can work together in Syria.
Among the key questions, top American lawmakers and foreign policy analysts say, is whether the United States, Europe, and Russia can find common ground on Syria.
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Can the West and Russia bring their Middle East allies to the bargaining table?
What would be the political future of Assad? How do all sides safeguard civilians from continuing attacks? Will the US and Russia coordinate military operations against the Islamic State of Iraq and the Levant (ISIL)?
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"It's a hard one," Democrat Senator Richard Durbin told Al Jazeera. "The White House has been looking for a way to make a meaningful difference. I don't know if there is an opening here with Putin. I can't tell."
Senator John McCain, the Republican chairman of the Senate Armed Services Committee, also expressed doubt.
"Putin's interests are to keep Bashar Assad in power - the same guy that has slaughtered tens of thousands of his own people," McCain told Al Jazeera.
"If we think that somehow we are going to have some Faustian bargain with the Russians, it will be a tragic mistake."
Russia, however, was key to the multilateral Iran nuclear deal, reached among the US, China, France, Germany, UK, Russia and the EU. In their most recent direct conversation, a telephone call in July, Obama thanked Putin for Russia's constructive role in two years of nuclear talks.
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Many observers now expect to see a window opening for regional discussions on Syria.
"You are going to see a great flurry of diplomatic activity in the Middle East, because everybody knows that the deal is not the answer to all the problems," said Jean-Marie Guéhenno, a former senior UN peacekeeping official now president of the non-profit International Crisis Group in Brussels.
"Now is the time to begin to build a diplomatic framework in the Middle East that at the moment doesn't really exist," Guéhenno said at a recent forum in Washington.
The refugee situation in Europe has given new urgency to the search for answers to what has been a horrific conflict and humanitarian disaster. Nearly 500,000 refugees have crossed the Mediterranean Sea to get to Europe so far in 2015, according to the International Organization for Migration.
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In Syria, both government and opposition forces have committed war crimes and indiscriminate attacks on civilians, according to the UN's latest report. More than 230,000 have been killed and four million refugees are in Turkey, Lebanon and Jordan.
"The international community cannot be blind to the cycle it has allowed to prevail for so many years," Paulo Sérgio Pinheiro, chair of the UN Human Rights Council's investigation into the violence in Syria, said last week in Geneva.
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The Obama administration's policy since 2011 has been to condemn the Syrian government and assert that Assad himself must be removed as part of a future political transition.
Early in the conflict, the US provided covert support to opposition groups. After the emergence of ISIL, Obama authorized a limited bombing campaign in Iraq and to a lesser extent in Syria.
Coordinated US air support for Kurdish forces has been successful in northern Syria. US Special Forces have conducted a limited number of specific missions.
But a training programme for so-called moderate Syrian fighters has failed to produce a viable US-backed ground force, the head of the US military's Central Command General Lloyd Austin admitted to Congress recently.
In Washington, Obama's Republican critics see presidential weakness and a failure to lead on Syria. The lack of a coherent policy has prompted a growing debate in foreign policy circles about what more the US can or should do.
"Here you have Iran and Russia teaming up to strongly beef up Assad's strength and yet there is no real US response other than, 'we are going to sit down and talk'," Senator Bob Corker, the Republican chairman of the Senate Foreign Relations Committee, told Al Jazeera.
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Former CIA director, retired General David Petraeus, the architect of the George W Bush administration's 2007 troop surge in Iraq, recommendedlast week the US impose restrictions on Assad's air force and create safe zones for civilians.
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The US should establish "enclaves in Syria protected by coalition air power, where moderate Sunni forces could be supported and where additional forces could be trained, internally displaced persons could find refuge and the Syrian opposition could organize", Petraeus said in Senate testimony.
Even if the Obama administration was willing to escalate US military operations in Syria - many analysts view Obama as risk-averse - Russia would be unlikely to go along with the establishment of no-fly zones by the US.
"They feel that once this is established, that inevitably the West will do more to push the Assad regime out and it will just be chaos," Mark Katz, a professor of international relations at George Mason University, told Al Jazeera.
Michael O'Hanlon, a senior fellow at Brookings in Washington, is proposing a concept of dividing Syria into protected regions, similar to Petraeus.
"What we need to be doing is thinking about first principles of a strategy that can be successful, and we really haven't done that for four and half years," O'Hanlon told Al Jazeera.
Source: Al Jazeera