Stacked containers sit among gantry cranes illuminated at night at Tanjong Pagar Container Terminal at the Port of Singapore in Singapore. (Seongjoon Cho/Bloomberg)

Secretary of State John F. Kerry sought to raise the stakes Wednesday in the debate over the Trans-Pacific Partnership, warning that U.S. leadership and credibility in Asia would be severely damaged if Congress fails to approve the largest regional trade accord in history.

The fate of the 12-nation pact, known as the TPP, will go a long way toward determining “whether the United States of America is an Asia-Pacific power or whether we are not — and the ‘not’ carries with it serious consequences,” Kerry said in a speech at the Wilson Center.

Kerry’s impassioned defense of the agreement came two days after the two major-party nominees for president, Republican Donald Trump and Democrat Hillary Clinton, criticized the impact of multilateral trade pacts on American workers and denounced the TPP in a nationally televised debate.

Though polls show that a majority of Americans favor international free trade, widespread skepticism in manufacturing-heavy swing states, including Ohio and Pennsylvania, has put the future of one of President Obama’s top economic priorities in doubt. Republican leaders in Congress have said it is unlikely that the pact would be considered for a ratification vote before Obama leaves office in January.

The U.S. and 11 other nations have come up with a trade deal after years of negotiations. But what's in it, who hates it, and what happens next? (Gillian Brockell/The Washington Post)

Kerry called on lawmakers to approve the deal in an expected brief lame-duck congressional session after the Nov. 8 elections. Without naming Trump or Clinton, he said that trade skeptics who have warned of economic “doom and gloom . . . have consistently been proven wrong.”

The secretary cast the trade accord as a crucial strategic initiative underpinning the Obama administration’s attempt to “rebalance” U.S. foreign policy away from the Middle East and Europe and toward greater attention on Asia.

The Obama administration spent five years negotiating the deal, which covers countries that account for about 36 percent of the world’s gross domestic product. The pact includes advanced economies such as Japan, Canada and Singapore as well as some of the world’s least developed, such as Malaysia and Vietnam.

“We can’t withdraw from the TPP and still be viewed as a central player in the Pacific Rim and an undisputed force for peace and prosperity across the globe,” Kerry said. “Our partners worldwide need to know they can always look to us for principled leadership, with no uncertainty and no doubt.”

The TPP is a sprawling 30-chapter accord that addresses tariff reductions for agriculture and automobiles, as well as intellectual-property rights for movies and pharmaceutical drugs, the free flow of information on the Internet, wildlife conservation, online commerce and dispute settlement practices for multinational corporations.

The debate over trade has become central to the 2016 campaign. Trump’s opposition to the TPP has muted support among GOP leaders who had overwhelmingly backed legislation last year that granted Obama greater trade negotiating powers. Trump blames past trade deals for obliterating the U.S. manufacturing sector.

Clinton had been a forceful advocate for the deal while serving as secretary of state in Obama’s first term. But she reversed her position during a hard-fought Democratic primary campaign against Sen. Bernie Sanders (Vt.), who has vehemently opposed free-trade pacts.

Secretary of State John Kerry (Jason Decrow/AP)

During the debate Monday, Trump noted that Clinton had referred to the TPP as the “gold standard” of trade deals while serving in the State Department. Clinton responded that she had raised concerns over the deal in her book, “Hard Choices,” which was published after she left office, and formally renounced the pact after the final terms were announced last fall.

“Is it President Obama’s fault?” Trump asked her. “Because he’s pushing it.”

The administration has vowed to continue lobbying Congress, and Kerry’s speech was the latest in a coordinated campaign to promote the deal. Obama met with a bipartisan group of political and business leaders in the Oval Office to talk about the merits of the TPP two weeks ago.

On Tuesday, U.S. Trade Representative Michael Froman published a commentary in the Houston Chronicle warning that the United States risked ceding ground to China. Although China is not a member of the TPP, Beijing is negotiating a separate regional trade pact in Asia that does not include the United States.

“If Congress delays, China will be all too glad to fill the vacuum and even our closest allies will feel the need to move on,” Froman wrote.