US president Barack Obama's call for "fast track" negotiations for the Trans-Pacific Partnership (TPP) has cleared a key hurdle in the US Senate, paving the way for a final vote on the legislation.

The Senate is likely today to grant Mr Obama the power to speed trade deals through Congress, including the TPP, later this week.

If that happens, the fast-track measure would then go to the White House for Mr Obama's signature.

That would be a major win for the Democratic president and a setback for one of his allies, US labour unions that have campaigned against the TPP out of fear it could destroy US jobs.

The Senate was also expected to vote soon on legislation to extend and expand a program of federal aid for workers hurt by international trade.

A house vote on fast track is possible on Thursday, if the Senate approves it.

"Our goal is to get [both measures] to the president's desk this week," Republican House speaker John Boehner said in a statement.

The White House said it wants both bills to reach the president's desk to be signed into law.

But a spokesman offered no clarity on whether the president would sign one without the other, or wait for them both to arrive.

Spokesman Josh Earnest said Mr Obama had no set timeframe for signing the bills but the president is expected to approve both.

Vote to limit debate barely scrapes through Senate

The Senate voted 60-37 on Tuesday to limit debate on the fast-track measure.

That just barely satisfied the 60-vote threshold needed after two senators who supported the bill on its first run through the Senate a month ago — Republican Ted Cruz and Democrat Ben Cardin — changed their votes to "no".

"Today is a very big vote. It's an important moment for the country," said Senate majority leader Mitch McConnell, the chamber's top Republican, in urging senators to support the 12-nation TPP, a central part of Mr Obama's foreign policy pivot to Asia.

Democrat Sherrod Brown, who voted "no" on fast track, said the trade deal would benefit companies at the expense of workers.

"This is a day of celebration in the corporate suites of this country," he said after the vote.

Fast-track legislation would let lawmakers set negotiating objectives for trade deals, including the TPP, but restrict them to yes or no votes on final agreements.

That would leave just one section of the four-part trade package outstanding, a bill to strengthen customs and enforcement that must be considered by a joint committee of lawmakers from both chambers.

Trading partners want fast track enacted before finalising TPP, the biggest trade deal since the North American Free Trade Agreement liberalised commerce between the United States, Canada and Mexico two decades ago.

Reuters