By Emily Stephenson

WASHINGTON (Reuters) - U.S. Senator Elizabeth Warren hit back at President Barack Obama in their tussle over "fast-track" authorization to negotiate a Pacific Rim trade treaty, a power she says could be used in the future to weaken Wall Street reforms.

The president, who wants expedited negotiating power to streamline the passage of trade deals through Congress, said last week that Warren's claims were "absolutely wrong."

Warren, a Massachusetts Democrat and prominent liberal voice, stuck to her argument in an interview published on Monday with a Washington Post blog, saying Obama should release details of the Pacific trade talks so legal experts can determine if a pact could be used to weaken U.S. bank rules.

"If the president is so confident it's a good deal, he should declassify the text and let people see it before asking Congress to tie its hands on fixing it," Warren said in the interview with the Plum Line blog.

Also on Monday, the second-ranking Senate Democrat raised doubt there were enough votes among Democrats to propel the fast-track bill over a procedural hurdle on Tuesday.

"At this point it's very questionable" that Senate Majority Leader Mitch McConnell, a Republican, can get the 60 votes needed to limit debate on whether to formally bring fast track onto the Senate floor, Dick Durbin said.

McConnell has until mid-afternoon on Tuesday to find those votes in the 100-member Senate.

Senate Democrats want the bill to be coupled with three other trade measures, including legislation providing training to U.S. workers who lose their jobs as a result of trade deals. They also want to link it to a measure stopping China from manipulating its currency to get a leg up on trade.

Senate Finance Committee Chairman Orrin Hatch said late on Monday: "There is no compromise that can be reached" rolling all four trade bills into one. But he and Durbin indicated there could be ways to craft a different compromise.

DEMOCRATS SPLIT ON TRADE

The dispute between Obama and Warren, both Democrats, reflects a split within the party over the White House's trade agenda, which includes the 12-nation Trans-Pacific Partnership, stretching from Japan to Chile.

On Monday, the White House stood firm in what it called a "substantive disagreement."

"The president was blunt about the fact that some of her facts were wrong," White House spokesman Josh Earnest told reporters.

Warren has said fast-track authority, which would mean Congress could approve or reject deals like the TPP but not change specific provisions, could be used by a future president to weaken Wall Street reforms that she championed.

Obama, in an unusual alliance with congressional Republicans, says the pact would open new markets around the Pacific Ocean for U.S. goods. Many Democrats fear the deal will hurt American workers.

Warren joined with 13 other Democratic senators in writing to the U.S. Trade Representative to say countries like Vietnam, Malaysia, Brunei and Mexico should have to change their labor laws before getting any trade benefits.

"American workers cannot compete against workers in these countries where fundamental worker rights are not protected," said the May 8 letter, released on Monday.

Among the signatories was Maryland's Ben Cardin, one of seven Democrats who backed fast-track legislation during debate in the Senate Finance Committee.

(Reporting by Emily Stephenson; Additional reporting by Krista Hughes and Richard Cowan; Editing by Kevin Drawbaugh, Jeffrey Benkoe, Dan Grebler and Peter Cooney)