PHOTO: VP Biden briefs members of Congress on Syria today in the Situation Room of the @whitehouse. pic.twitter.com/B7jmGLujmc — Office of VP Biden (@VP) September 5, 2013

President Barack Obama's outreach to wary lawmakers on Syria did not stop at the water’s edge, the White House let it be known on Thursday as he met in Russia with world leaders. And Vice President Joe Biden briefed a small group of Senators and Representatives in the White House's "Situation Room."

In all, the White House's aggressive courtship has reached more than one in three members of Congress, which could vote as early as next week on whether to give its assent to his plan for military strikes. Congressional vote-counters say defeat is a very real possibility.

The White House declined to identify the lawmakers Biden briefed, but his official Twitter account posted a picture that appeared to show Democratic Senators Al Franken of Minnesota, Heidi Heitkamp of North Dakota, as well as Democratic Representatives Joe Garcia and Joseph P. Kennedy III listening to Biden in the super-secure basement room.

Deputy national security adviser Ben Rhodes told reporters traveling with Obama at the Group of 20 summit that the president “made five calls to a bipartisan group of senators” during a Wednesday stop in Sweden.

Were they supporters of his call to strike Syrian strongman Bashar Assad’s forces? Wavering or on the fence? Leaders who might help plot parliamentary strategy? Did five calls mean five senators? White House aides declined to say.

But even as Obama planned to court fellow heads of state and government at a dinner hosted by Russian President Vladimir Putin — enemy No. 1 of Obama’s push to punish Assad for allegedly massacring civilians with chemical weapons on Aug. 21 — the White House shared details of his outreach.

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A White House official, who described the campaign on condition of anonymity, said Obama and top aides had discussed Syria with at least 60 senators and 125 House members over the past two weeks. That sets the beginning of the outreach about one week before the president formally announced on Saturday that he would seek congressional authorization to use military force. It was not clear whether feedback from lawmakers played a role in that decision.

On Wednesday, White House chief of staff Denis McDonough held conference calls with the Progressive Caucus and the Hispanic Caucus. Deputy national security adviser Tony Blinken held one with Jewish House members. And Obama and other top White House aides placed more than 25 individual calls to Democratic and Republican members of both chambers.

Vice President Joe Biden, Secretary of State John Kerry, Defense Secretary Chuck Hagel, national security adviser Susan Rice, U.S. Ambassador to the U.N. Samantha Power, and other top aides have also joined in the effort.

Obama is expected to court Group of 20 leaders on the issue at a formal dinner late Thursday. And Kerry will take the administration’s argument to Europe on Sept. 6-9, when he is expected to meet in Vilnius, Lithuania, with his European counterparts. He is also planning stops in France on Sept. 7 and London on Sept. 9.