Looking to head off a crisis in Asia akin to the war in Ukraine, U.S. President Joe Biden on Monday used his first in-person summit with Prime Minister Fumio Kishida to address Beijing’s “increasingly assertive behavior,” with the American leader appearing to break with decades of policy by vowing to defend Taiwan if it were to be invaded.

Biden said China was “already flirting with danger” by repeatedly conducting military exercises in the vicinity of democratic Taiwan, part of actions that some observers fear could be a precursor to invasion.

Asked if the United States would be willing to get involved militarily to defend Taiwan, Biden — who has in the past made gaffes on the subject — delivered a curt response during a post-summit news conference.