President Obama delivers remarks on trade at Nike's corporate headquarters in Beaverton, Ore., in 2015. (Jonathan Ernst/Reuters)

The Obama administration is fighting back against an anti-free trade mood on the 2016 campaign trail, arguing that the United States' credibility and prestige in Asia is at stake in the debate over a Pacific Rim trade deal that the president has made a top priority in his final year.

"Failure to move forward ... would be a profound setback for American interests in the region," Ben Rhodes, a White House deputy national security adviser, said Tuesday of the 12-nation Trans-Pacific Partnership. "It would be a signal that we do not have staying power and cause countries to hedge on their alignment with the United States."

The administration is running out of time to get the accord ratified by Congress and faces an uphill slog to win approval with the leading presidential candidates in both parties opposed to the deal. Republican front-runner Donald Trump has denounced free trade deals as harmful to American workers and a drag on the U.S. economy. Democratic front-runner Hillary Clinton, who supported the TPP as secretary of state under Obama, has come out against the TPP under pressure from the left, including labor unions and her opponent Sen. Bernie Sanders (Vt.), who also opposes it.

But in a conference call with reporters, administration officials warned that China is poised to step into an economic and leadership void if the U.S. falters in the pact with 11 other nations, including Japan, Malaysia, Vietnam and Australia. While Trump and Sanders have called outsourcing and trade imbalances with China  detrimental to the United States, White House allies said that the economic competition from China, which is not included in the TPP, is a reason to endorse the deal.

"If one is concerned about China's behavior ... if they are a challenge to U.S. interests, the importance of TPP from a security and foreign policy perspective cannot be understated," said retired Lt. Gen. Dan Christman, who was among a group of former military officials who met with White House aides Tuesday to discuss the national security aspects of the trade pact.

Obama aides have said the U.S.-led accord would help establish rules for regional commerce and higher standards for workers and the environment, while integrating the United States more closely with countries that include longtime allies, such as Japan, and rivals, such as Vietnam. The president is scheduled to travel to those two countries in May, and aides said he will emphasize the importance of the deal during his visits to both.

"Should this deal not take place, given the heavy lifting from the other countries, Vietnam in particular, to sign up, this would reflect, in my judgment, an enormous strategic setback," Christman said.

The White House had hoped Congress would vote on the TPP by summer, but the opposition to free trade deals on the campaign trail has made that time frame unlikely. Republican leaders in Congress, who had largely supported the deal when lawmakers voted last year to grant Obama additional trade promotion authority, have since expressed concerns about portions of the pact, while some rank-and-file GOP members have said they don't support it.

Administration officials are eying the lame-duck session of Congress after the November elections as the final opportunity to complete the deal during Obama's tenure.