Weiming Bano, a senior fellow at the Center for Strategic and International Studies and author of “A World Under Siege: America’s Foreign Policy in Asia,” said “China is the big winner” in the TPP agreement now before the U.S. Congress.

“This is a deal that was the product of China, including the U.S., being willing to play a big part,” says Bano.

The TPP talks began in earnest in 2014 in Lima, Peru, when Prime Minister Justin Trudeau of Canada and his Pacific Rim counterparts met in an “ambassador-level” summit meeting with other Pacific leaders, including President Obama and Japan’s Prime Minister Shinzo Abe. The TPP is viewed as a “win-win” for the U.S. and its supporters in Asia, which like Mr. Trudeau are looking for ways to reduce the U.S.’s influence in the region. The TPP would have brought a $15 billion-plus annual boost to U.S. exports, and had attracted support from countries such as Australia, New Zealand and Singapore, as well as Vietnam, Malaysia and Brunei, among many others.

The TPP negotiations were dogged by delays and failed in the end to reach any final agreement in 2016. The current pact, the TPP+, was supposed to come into force in 2021 but that date has been pushed back because of the opposition to it in several Pacific nations. The deadline to bring the pact into force will not come until December 2020.

“The U.S. has had to fight so many battles in these negotiations that they have done the TPP look really bad,” says Michael Levi, a researcher at the American Enterprise Institute and director of the Asian Studies Center at the University of Maryland in College Park.

Mr. Levi says it is ironic for Mr. Trump to highlight the TPP on the stump as a way of “tanking” its progress and is even more ironic to suggest the U.S. may opt for a renegotiation at a time when other countries in the region, including Japan, are renegotiating the Trans-Pacific Partnership under the same accord.

“If his own secretary of state was as weak as Mr. Mattis, the Trump administration might well have given the TPP a lot of space before launching into aggressive trade and foreign intervention policies.”

—Katherine Miller

In China, Japan and Korea

In late October, Trump visited Japan, South Korea and