The White House also expressed optimism that Congress would overturn the “don’t ask, don’t tell” policy, despite key GOP senators giving no indication that they would agree.
A test vote was scheduled for late Wednesday on a defense policy bill that includes the repeal provision.
“The president is hopeful, and encouraging Democrats and Republicans to get behind that repeal,” said White House spokesman Robert Gibbs.
Advocates for overturning the law say they are confident that at least 60 senators are on their side, giving Democrats a filibuster-proof majority to pass the measure.
But Republicans, including Maine Sen. Susan Collins and other GOP senators who support repeal, have united to block previous attempts to advance the legislation. They say the bill requires more debate time than Senate Majority Leader Harry Reid has allowed.
In recent days, GOP senators have said no bill should be considered before tax cuts and government spending are addressed.
Reid, D-Nev., told reporters Wednesday that he is trying to negotiate a deal with Collins that would allow more than a dozen amendments on the bill and extra debate time for Republicans if they wanted it.
Reid’s aides said they expected Collins would swing behind the proposal, especially now that a deal had been struck with the White House on tax cuts and the Senate was awaiting House action on government spending.
A spokesman for Collins, Kevin Kelley, would only confirm that she was in talks with Reid on the subject.
Reid said Republicans had run out of excuses to block the bill.
“Throwing up these artificial roadblocks is just foolishness,” Reid said.
Still, Reid’s decision to force a vote now on repeal was considered a gamble.
If it fails, it would be considered dead for the year. The repeal effort would then face an uphill battle come January when Republicans take control of the House and increase their numbers in the Senate.
If it passes, the Senate would spend the next few days debating the bill before a final vote is cast.
At least four Senate Republicans – Lisa Murkowski of Alaska, Scott Brown of Massachusetts, Susan Collins of Maine and John Ensign of Nevada – have said they think the law should be overturned.
Conservative Democrats who were initially reluctant on the matter, including Sen. Mark Pryor of Arkansas, have also said they would vote to lift the ban now that a Pentagon study concluded it wouldn’t hurt military effectiveness.
Advocates for repeal said privately they thought Wednesday’s vote was doomed to fail. Publicly, gay rights groups called on President Barack Obama to use his power to ensure the vote succeeded.
“The president set a course for repeal during his State of the Union address and this Senate vote may be the steepest hurdle of this 17-year fight,” said Christopher Neff, deputy executive director of the Palm Center at the University of California, Santa Barbara.
“This is the president’s vote and his leadership can make the difference today,” Neff said in a statement e-mailed shortly after Reid’s announcement.