The Senate would then begin debate Thursday evening on trade promotion authority.

The agreement gives Democrats a chance to demonstrate broad, bipartisan support for a get-tough approach on countries that intentionally keep the value of their currency low to make their exports cheaper, which then effectively raises the cost of American-made goods. But if that separate bill can get through the House, it would then be vetoed by the president, who believes it would destroy the trade talks.

For the most ardent opponents of Mr. Obama’s trade push, the deal means delay, which can be perilous for trade negotiators. Under the terms of the trade promotion legislation, Congress could not consider a final Pacific trade deal for four months after it was completed, pushing it further into the election season, when major legislative initiatives become far more difficult. Final negotiations would not begin unless and until Congress approved the accelerated authority.

Republicans succeeded in fending off a Democratic push to attach the currency measure to trade promotion authority itself. The measure has the support of a strong majority in the Senate, including Senator Rob Portman, Republican of Ohio and a United States trade representative in the administration of President George W. Bush. American automakers and some economists believe a currency measure is vital to a trade agreement that is intended to protect the interests of American workers.

Mr. Portman went to the Senate floor Wednesday evening and promised that he would push for a currency provision on the trade promotion bill itself. “Part of a level playing field is making sure countries don’t manipulate their currency,” he said.

But the White House fears that making the accelerated authority contingent on currency policy alterations could scare important partners from the negotiating table, including Japan, the second-largest Trans-Pacific partner.

Senator Mitch McConnell, the majority leader, insisted on a legislative approach that would “provide our Democratic colleagues with a sensible way forward without killing the bill,” he said as he presented the plan on the Senate floor.

For his part, Mr. Obama preserved a clean path toward the Pacific trade deal, which includes Australia, Brunei, Canada, Chile, Japan, Malaysia, Mexico, New Zealand, Peru, Singapore and Vietnam, as well as the United States. “Yesterday, we made it clear we didn’t accept merely a fast-track foreign trade agreements,” said Senator Harry Reid of Nevada, the Democratic leader. “We must also enforce the trade agreements we make. The proposal today provides that path forward.”