(Reuters) - Republican House Speaker John Boehner challenged Hillary Clinton on Sunday to help the White House get trade legislation through the U.S. Congress by speaking out in favor of it.

Lawmakers are debating whether to give President Barack Obama "fast-track" authority to negotiate deals such as the 12-nation Trans-Pacific Partnership (TPP). Trade is a rare issue on which the White House enjoys support from Republicans, but many Democrats are opposed.

"She can't sit on the sidelines and let the president swing in the wind here," Boehner said on NBC's "Meet the Press."

Boehner said Clinton, 2016 presidential contender and a former secretary of state, supports both fast-track authority and the TPP, but "she just won't say so."

The White House says free-trade deals open up new markets to U.S. exports and help businesses compete abroad. But many Democrats and their supporters, including labor unions, say the deals help big corporations at the expense of American jobs.

Clinton has not stated a clear position on either fast-track legislation or the negotiation of the TPP deal with Asia. She recently said that any trade deal "has to produce jobs and raise wages and increase prosperity and protect our security."

Representative James Clyburn, a member of House Democratic leadership, said this week he didn't know whether there were even 20 votes out of a total of 188 Democrats in the House for fast-track authority, also known as Trade Promotion Authority (TPA).

"The fact is that the president needs her help in order to get Democrat votes in the House and Senate to get this passed," Boehner said on Sunday.

There are 244 Republicans in the House, but not all of them support trade deals; Boehner's allies estimate that he may be only able to get 180 to 200 Republican votes for TPA.

Boehner told NBC that every Democratic leader in Congress is opposed to the president's position.

"We've got the majority here in the House and the Senate, but we can't do this by ourselves," Boehner said of the Republicans.

Clinton has also been criticized by Republican Jeb Bush, a potential presidential candidate, for her reticence on trade.

(Reporting by Susan Cornwell; editing by Jane Baird)