Trump is silent on Taiwan after talking to Xi—and that is fine with Taipei

But with China’s military growing stronger and leader Xi Jinping on a mission to tell the world that Taiwan belongs to Beijing—a message he delivered to President Trump in a phone call Monday—the question has resurfaced: Is saying little saying enough?

The view from Taiwan’s leadership: Trump’s silence speaks volumes.

“The relationship between Taiwan and the U.S. is rock solid," Taiwan President Lai Ching-te said Wednesday, after declaring that he would seek a $40 billion special budget for military spending to deter China.

U.S.-Taiwan cooperation during Trump’s second term has been “nonstop," Lai said. “That’s why we’re confident about the future of U.S.-Taiwan relations."

Taiwan’s survival depends on U.S. military support. That makes Trump’s public silence, coupled with his willingness to turn away from traditional U.S. alliances, a cause for concern for some in Taipei.

The fear is that Trump could modulate support for Taiwan to reach a trade deal with China, just as he has used U.S. support for Ukraine as leverage for a potential peace deal with Russia.

“Taiwanese people want to hear, ‘Of course America has your back,’ but America is not going to say that," said Lev Nachman, who teaches political science at National Taiwan University. “Trump’s not going to say that."

When Trump and Xi met in South Korea in October, at an upbeat summit that focused on progress in trade agreements, the contentious topic of Taiwan didn’t come up. Asked during a CBS’s “60 Minutes" interview after meeting with Xi if he would order U.S. forces to defend Taiwan, Trump replied: “You’ll find out if it happens. And he understands the answer to that."

With the two leaders planning to meet again in China in April, Xi made a move on Monday to drive a wedge between the U.S. and Taiwan. The Chinese leader emphasized to Trump his view that Taiwan must “return" to China, which claims the island as its own territory.

Trump, posting on social media about the call, made no mention of Taiwan. “Our relationship with China is extremely strong!" he wrote.

Xi’s message to Trump followed two weeks of Chinese diplomatic attacks against U.S. ally Japan over Prime Minister Sanae Takaichi’s comment that her country could be pulled into a war over Taiwan.

Following his talk with Xi, Trump set up a call with Takaichi in which, The Wall Street Journal reported, he advised her not to provoke Beijing on the question of Taiwan’s sovereignty. Takaichi’s office denied that Trump made such a remark.

Some analysts described Trump’s public silence on Taiwan as a source of leverage for the U.S. side.

“The U.S. has kept approving sizable arms packages for Taipei even as economic talks continue," said Craig Singleton, a senior fellow at the Foundation for Defense of Democracies, a Washington-based think tank. “Xi pressing Taiwan on this call reflects frustration that Trump is not giving China the rhetorical shift it wants."

Taiwan’s security remains a focal point of U.S. military strategy in the Pacific. Military installations in South Korea, Japan and Guam maintain a U.S. footprint intended in part to deter Beijing.

The U.S. approved new arms sales to Taiwan this month, a first in the second Trump presidency. Taiwan has commissioned its new Abrams tanks purchased from the U.S. and is getting up to speed on the use of its new U.S.-made Altius-600M attack drones. Members of Taiwan’s military routinely receive U.S. training, including a unit of marines that recently trained in Guam.

Still, the Trump administration has pressed Taiwan to spend more on its own defense—making every defense dollar spent by Taipei an argument for sustained U.S. support. Lai has pledged to increase the military budget to 5% of GDP by 2030, from the 3.32% set for next year’s budget.

The question of American support also has political ramifications. Public backing for Lai’s ruling Democratic Progressive Party is built in large part on the argument that the island must prepare to battle China and deflect Beijing’s “gray zone" efforts to get Taiwan to submit without a fight.

Former President Joe Biden said, and repeated, that the U.S. would defend Taiwan in the event of a Chinese invasion. White House staff walked back his comments—all four times.

Trump has consistently adhered to the policy of strategic ambiguity, said Marvin Park, a nonresident senior fellow at the Atlantic Council who was director for Taiwan affairs in Biden’s National Security Council.

“Between Trump 1 and Trump 2, Trump has never willy-nilly just haphazardly or flippantly talked about Taiwan," Park said. “You don’t want Trump to talk about Taiwan until he is ready to talk about Taiwan."

National security officials in Taipei said that they interpret Trump’s public silence as a sign that Washington doesn’t agree with Xi’s claim to the island. Trump has previously said he received assurances from Xi that China won’t attack Taiwan as long as he is in the White House.

Even so, the worry lingers on an island whose survival ultimately depends on the U.S. military: What if China attacks and the U.S. doesn’t come to the rescue?

The question itself has a real effect on Taiwan’s security, said Nachman. While U.S. silence may deter China, it can also weaken public resolve, he suggested.

“Whether or not we believe America is coming or not has a very big effect on people’s willingness to defend Taiwan," Nachman said.

Write to Joyu Wang at joyu.wang@wsj.com