Following days of obstruction from lawmakers in President Barack Obama's own Democratic party, the US Senate advanced contentious legislation allowing him to swiftly finalize a landmark Pacific trade pact.
The 65 to 33 vote marked a victory for the White House and free-trade Republicans who had united in an effort to press ahead with Obama's biggest domestic legislative priority in the remaining 20 months of his presidency.
But it belied what may be a tough battle to get the divisive bill -- backed by big business but opposed by unions -- across the finish line and to the president's desk.
Thursday's vote merely opened debate on so-called "trade promotion authority," which would allow Obama -- and his successor -- to negotiate international trade accords and present them to Congress for a yes-or-no vote, with lawmakers prevented from making any changes.
The measure also provides assistance for US workers hurt by globalization, and sets 150 objectives for Washington to negotiate into the accords, including provisions on human rights.
Debate begins in earnest Monday, and a final Senate vote on TPA is expected next week.
Supporters argue that the 12-nation Trans-Pacific Partnership, and a US-Europe trade accord currently under discussion, would together create 1.4 million American jobs and level the playing field for US exports abroad.
Democrats blocked TPA from advancing Tuesday, arguing the bill ignored some of their priorities, including ensuring that American jobs were protected from unfairly priced imports.
But intense negotiations broke the impasse, and the Senate also voted Thursday to impose strict enforcement measures on international trade, including currency manipulation restrictions.
That bill now heads to the House of Representatives, where its chance of passage took a hit when Speaker John Boehner dismissed as "laughable" the prospect of Congress legislating currency valuations between countries.
The measure seeking to prevent some governments from manipulating their currency's value in order to gain trade advantage is aimed at Asian giants China and Japan.
The currency bill is "a shot across China's bow that we're not going to just sit there and do nothing," Democratic Senator Chuck Schumer said.
"Americans should not be patsies for other countries cheating," added Senator Sherrod Brown.
The bill also closes a child labor loophole, and beefs up other customs enforcement priorities including antidumping rules.
- No poison pills? -
The White House and Republican leaders had warned that including such a measure directly in the TPA bill could jeopardize the broader legislation and throw the entire Pacific accord into doubt.
"Under our plan, the Senate will avoid the poison pills that had been floated," while allowing senators "to express themselves without endangering more American trade jobs," Senate Majority Leader Mitch McConnell said.
But TPA itself will face opposition in the House, where Democratic leader Nancy Pelosi said members of her caucus were expressing "unease" with a potentially years-long process that could "provide carte blanche for agreements unknown, for countries to be determined, for a time in perpetuity."
Obama, speaking at Camp David outside Washington, thanked senators for beginning the TPA debate but acknowledged the difficulties in selling the trade deal to skeptical Democrats.
"I want to keep on trying to make the case and provide them the information they need to feel confident that despite the fact that there have been very genuine problems with some trade deals in the past, the approach that we're taking here I think is the right one," he said.
Obama stressed the trade accord, with partners as diverse as Japan, Vietnam and Chile, would be a victory not just for big US businesses, but small enterprises and "ultimately, American workers."
But independent Senator Bernie Sanders said the accord would only fuel US job losses.
"It will be a great program for them," Sanders said of American corporations. "It will only accelerate their ability to shut down plants in America and move to low-wage countries abroad."