Recent comments by Donald Trump that arms sales to Taiwan are a “very good negotiating chip” in the United States’ dealings with China are heightening anxieties on the island democracy that Beijing claims as its own.

Trump made the comment in a Fox News interview with Bret Baier that aired right after the U.S. president wrapped up a high-stakes visit to China on Friday.

China sees Taiwan as a breakaway province, to be retaken by force if necessary. The U.S., like all countries that have formal ties with Beijing, doesn’t recognize Taiwan as a country but has been the island’s strongest backer and arms supplier.

Trump is now suggesting that is open to negotiation.