U.S. Senate may vote on Yellen in rare Saturday session - aide

WASHINGTON (Reuters) - The Democratic-led U.S. Senate may vote in a rare weekend session on Saturday on whether to confirm Janet Yellen to head the Federal Reserve, a senior aide said on Thursday.

The Senate appears certain to confirm Yellen, the Fed's vice chair, to replace Ben Bernanke, whose term expires next month.

Democrats had hoped to vote on Yellen's confirmation on Thursday or Friday, but have been unable to reach a time agreement with Republicans to speed up the process, the aide said on condition of anonymity.

Unless such an agreement is reached, the Senate will begin consideration of the first of four of President Barack Obama's pending nominees at close to midnight on Thursday (0500 GMT on Friday) - Alejandro Mayorkas as deputy secretary of the Department of Homeland Security.

Under a tentative schedule and working around the clock, the Senate would vote to confirm Mayorkas before dawn on Friday, followed later in the day by John Koskinen to head the Internal Revenue Service and Brian Davis to be a federal judge in Florida.

The confirmation vote on Yellen is now expected to occur at about 6 p.m. on Saturday (2300 GMT), the aide said.

At that point, the Senate could begin consideration of six more nominees, all of them for relatively lower level posts.

The stage was set for this confirmation rush when Democrats changed the Senate rules last month to strip Republicans of their ability to block most of Obama's nominees with procedural roadblocks known as filibusters.

The change, however, did not strip Republicans of their ability to slow down matters by refusing to yield back any of their allotted debate time. (Reporting by Thomas Ferraro; Editing by Chizu Nomiyama and Paul Simao)