But the welcoming handshake may have been where the pleasantries ended. In other venues, the two nations were repeatedly bumping heads.
Russia's foreign ministry, in a statement Friday, said a U.S.-led strike would mark "a new dangerous turn" in the crisis, risking the release of chemical weapons or their possession by terrorists. And the head of the foreign affairs panel in Russia's lower house of parliament, Alexei Pushkov, blasted Obama on Twitter as having "completely transformed into a president of war."
Meanwhile, the Kremlin said Russia was boosting its naval presence in the Mediterranean Sea, moving in warships into the area and stoking fears about a larger international conflict if the United States orders airstrikes.
Even at home, there was far from a consensus that an American strike on Syria was the best course of action. Awaiting Obama upon his return was an equally fractious debate in Congress over whether to authorize the limited military action he was proposing.
Pulling out all the stops, Obama was working the phones from Europe and appealing for support from leery lawmakers, Democratic and Republican alike. And he called off a planned trip to California next week, opting to stay in Washington to keep up the pressure on Congress to say yes.
As top national security officials continued to brief Congress on the accusation against Assad and the proposed response, a measure authorizing Obama to act was advancing tenuously through the Senate, winning approval from a foreign relations panel Wednesday and heading to the Senate floor. The measure's prospects were dicier in the Republican-controlled House.
In an unusual turn of events, Senate Majority Leader Harry Reid and House Speaker John Boehner both said that a delegation of Russian lawmakers had sought to meet with them to discuss Syria. Both leaders, who are supporting Obama's call for a strike, turned down that invitation, aides said.
"I don't know that the Russians have anything to add to the debate in the United States, given that we know where Russia stands," said Rhodes, the Obama aide.
Associated Press writer Angela Charlton contributed to this report.