Taiwan’s president on Sunday stressed that arms purchases from the United States are “the most important deterrent” of regional conflict and instability, after President Donald Trump called into question continued U.S. support of Taiwan following his visit to China.

U.S. arms sales to Taiwan and security cooperation between the two sides are not only governed by law but also a catalyst for regional peace and stability, President Lai Ching-te said in a statement.

“We thank President Trump for his continued support for peace and stability across the Taiwan Strait since his first term, including the continuous increase in the scale and amount of arms sales to Taiwan,” he said.

His statement came days after Trump raised doubts over his willingness to continue to sell arms to Taiwan, the island democracy that China claims as its own breakaway province, to be retaken by force if necessary.

The U.S., like all countries that have formal ties with China, doesn’t recognize Taiwan as a country but has been the island’s strongest backer and arms supplier. Washington is bound by its own laws to provide Taiwan with the means to defend itself and sees all threats to the island as a matter of grave concern.

Trump rattles Taiwan with ‘bargaining chip’ comment

Trump already approved in December a record-breaking $11 billion arms package to Taiwan including missiles, drones, artillery systems and military software.

In an interview aired Friday on Fox News, just as Trump wrapped up a high-stakes visit to China, he said he has yet to greenlight a new $14 billion arms package to Taiwan and that it “depends on China.”

“It’s a very good negotiating chip for us frankly,” he said.

His comments raised concerns on the island, which the Taiwanese government has sought to disperse, noting that the U.S. official policy on Taiwan has not changed.