Sen. Bernie Sanders, the Democratic presidential frontrunner, said in an interview that aired Sunday that he would take military actions if China decided to strike Taiwan.

Sanders offered a glimpse into his position on national defense during a wide-ranging interview on “60 Minutes.” The Vermont senator cemented his status as the party’s frontrunner after a decisive victory Saturday in the Nevada Caucuses.

The Chinese consider Taiwan—a mountainous island with more than 23 million people—as a renegade province and lobbed ballistic missiles into the seas north and south of the island before its first fully democratic presidential election in 1996.

Beijing, which has been dealing with the coronavirus, has shown a willingness to flex its muscles in the region.

Anderson Cooper, a correspondent for the program, asked Sanders the type of international crisis that would force his hand to use military force. Cooper used a hypothetical scenario that involved a Beijing assault on Taipei.

“Yeah, that’s something…I mean, we’ve got to make it clear to countries around the world that we will not sit by and allow invasions to take place,” he said. Sanders said his criteria for military action would be threats against the U.S. and its allies. He said he would work to form alliances.

Earlier this year, Sanders criticized President Trump over his decision to kill Iran’s top general Qassem Soleimani in a drone strike. He said in an interview at the time that, as a senator, he would do everything in his power to prevent the U.S. from entering another war like Iraq.

Trump insisted that Soleimani’s killing made the U.S. safer. Mike Pompeo, the secretary of state, told News that the general was planning imminent attacks.