By Roberta Rampton

WASHINGTON (Reuters) - During a visit from Singapore's prime minister on Tuesday, President Barack Obama will extol the Trans-Pacific Partnership (TPP) trade deal and commit to getting the deal done, a top White House official said on Friday, even though Obama's fellow Democrats panned it at their convention this week.

Obama wants the U.S. Congress to approve the 12-nation trade deal, which he sees as a central part of his economic and foreign policy legacy, before he leaves the White House on Jan. 20.

Free trade deals have been blamed for U.S. manufacturing plant closures, job losses and stagnant wages. Obama has cast the TPP as righting the wrongs of past trade deals like the North American Free Trade Agreement with Mexico and Canada. Both countries also are part of the TPP.

Both Democratic presidential candidate Hillary Clinton and Republican Donald Trump oppose the TPP, and it has become a hot-button issue in the campaign to replace Obama.

Congressional leaders have been pessimistic about the odds of ratifying the deal either during the short session in September, or during the brief "lame duck" session after the Nov. 8 election.

When Obama rolls out the red carpet for Singapore Prime Minister Lee Hsien Loong on Tuesday, one of the main goals will be "lifting up the benefits" of the TPP, said Daniel Kritenbrink, top Asia policy adviser at the White House National Security Council.

"I predict he will also once again say to the prime minister that he's committed to getting TPP done and doing so before the end of his term," Kritenbrink told reporters on Friday.

"TPP is going to be great for the American economy, for American workers and American companies," Kritenbrink said, noting Singapore, a signatory to the deal, strongly supports it.

Trump has argued vociferously against multinational trade deals like TPP, saying he would prefer instead to have deals with specific countries one on one. On Thursday night at a rally in Cedar Rapids, Iowa, Trump said TPP should be rejected.

"I like trade where the United States makes a lot of money," he said.

Trump has been critical of Clinton, Obama's former secretary of state, and her vice presidential running mate Tim Kaine, for shifting their positions to oppose the trade deal.

Signs protesting the deal were prominent during the Democratic convention, which wrapped up on Thursday.

Kaine, a Democratic senator who had praised the TPP deal until he joined Clinton's ticket, told CNN on Friday that he was concerned the deal gives corporations the power to challenge trade practices, but not unions or environmental groups.

"The deal is going to come up for a vote and I can't vote for it with these secret courts that are open to the companies only," Kaine said in the interview.

Obama is "acutely aware" of the difficult election year politics for the TPP but that will not stop him from forging ahead, White House spokesman Eric Schultz told reporters on Friday.

"The president absolutely believes this deal should pass this year," Schultz said.

(Additional reporting by Steve Holland, Ayesha Rascoe, Richard Cowan and Mohammad Zargham; Editing by Jonathan Oatis and Jeffrey Benkoe)