Barack Obama and Russia's president Vladimir Putin completed a bilateral meeting on the margins of the G20 summit in Los Cabos, Mexico, on Monday with an agreement that there should be a cessation of hostilities in Syria.
But, crucially, Obama failed to secure the support of Putin for regime change in Syria. The US president had been seeking Putin's help in trying to persuade Syrian president Bashar al-Assad to relinquish power and leave the country.
A joint statement issued after their meeting said simply that the Syrian people should independently and democratically be allowed to decide their own future, but there was no joint call for Assad to stand down, as the White House has been urging.
Relations between the US and Russia have been cool for months over several issues, including continued concerns in Moscow over US missile plans for Europe as well as Syria.
The White House has publicly expressed frustration with Russia for its support for Syria, a Cold War ally, and its blocking of tougher United Nations actions against the Syrian government, such as sanctions.
There was little sign of rapprochment at Los Cabos, with Obama describing the discussion as 'candid', diplomatic-speak for disagreement. Their body language was poor too, with no smiles and little eye contact between the two in the short period in which journalists were invited in.
In the joint statement, the two leaders said: "In order to to stop the the bloodshed in Syria, we call for an immediate cessation of the violence and express full support for the efforts of the UN and Arab states joint special envoy Kofi Annan, including on moving forward on political transition to a democratic pluralist political system that would be implemented by the Syrians themselves in the framework of Syrian sovereignty, independence, unity and territorial integrity.
"We are united in our belief that the Syrian people should have the opportunity to independently and democratically choose their own future."
Neither leader mentioned Assad by name in their public remarks or in the joint statement issued after their meeting, thus avoiding any express reference to past US demands that Assad step down. There was also no mention of sanctions or a tougher arms embargo.
Obama said that he and Putin had "candid, thoughtful and through conversation" about various issues including Syria and Iran.
Without Putin's support, there is almost no chance of tougher UN action. Russia can use its security council veto to block any move.
The expression of support for the Annan plan was also hollow, as the UN and others have acknowledged it has so far been a complete failure.
The sense that Putin came out the meeting with more than Obama was enhanced by a comment from a Russian diplomat. Asked if the meeting was important for the Russians, the Russian diplomat said: "Yes, but even more for the Americans."
Putin has just come out of an election but Obama is facing one, making the US president the more vulnerable of the two. Syria is not yet an election issue but if television keeps showing footage of widespread killing in the country, it could easily become one.
John McCain, the Republican senator who was a presidential candidate in 2008, was dismissive of the joint statement by Obama and Putin. "I think it was the kind of statement you usually hear when there is no concrete agreement."
McCain called on Monday for US intervention by creating a safe haven for the rebels and to supply them with arms. He said on CNN it was an "unfair fight", noting reports of alleged supplies from Russia and Iran to the Syrian government.
The White House so far has shown an unwillingness for military intervention comparable to Libya last year and it had been hoping Putin might have helped in peacefully easing Assad from power.
Instead, Obama's failure to win over Putin leaves Syria facing the prospect of increasing violence.
The relationship between the US and Russia is extremely complex, although relations have cooled. Russia stepped in to help the US in Afghanistan by opening up its supply routes to the Americans after Pakistan closed its borders.
Relations have not been helped by a statement by the Republican presidential candidate Mitt Romney identifying Russia as the biggest single threat to the US.
Beyond Syria, Obama and Putin discussed diplomatic efforts to head off a confrontation with Iran. Obama said he emphasised a common approach to Iran, asserting there was "still time and space to resolve diplomatically" concerns about nuclear weapons.
Putin, a former KGB spymaster, is suspicious of US motives, especially after the Nato-assisted ousting of Libyan leader Muammar Gaddafi last year, and he has offered little sign of softening his stance on Syria.
Though Washington has shown no appetite for a Libya-style intervention, Russia is reluctant to abandon its Syrian ally, a longtime arms customer, and risk losing its last firm foothold in the Middle East.
As journalists entered the cramped hotel ballroom, the two leaders were leaning toward each other in discussion, neither smiling. Obama initiated a handshake for the cameras while the two remained seated.
Obama sometimes gestured toward Putin as he spoke but Putin sat more stiffly through the joint appearance. At the end of their statements, as reporters were being ushered out, both sat glumly watching and made no move to re-engage with each other.
Suspension of the UN monitoring mission in Syria over the weekend put added pressure on Obama and Putin, meeting for the first time since the Russian president's re-election, to act decisively to keep the conflict from spiralling into civil war.
In a statement that glossed over the intense differences between Russia and the US, British sources were arguing that the commitment to end violence could at least be construed as an advance on the Russian position at the UN Security Council only a month ago. At the time Russia was opposed even to a condemnation of the violence.
By Patrick Wintour and Ewen MacAskill