Secretary of State Rex Tillerson said Friday that “all options,” including a preemptive strike, are on the table when it comes to dealing with North Korea—the clearest signal yet from the Trump administration that it would consider taking military action against the nation.

At a joint news conference with South Korea’s Foreign Minister Yun Byung-se, Tillerson said the U.S.’s “strategic patience” approach was over and that it would not engage in talks with Pyongyang unless the hermit kingdom gives up its nuclear weapons.

“We’re exploring a new range of diplomatic, security, and economic measures. All options are on the table,” Tillerson said, adding that threats against the U.S. or South Korea “would be met with an appropriate response.”

“If they elevate the threat of their weapons program to a level that we believe requires action, that option is on the table,” he said.

Ruling out diplomatic talks will likely fuel fears that the U.S. is inching toward using military action, the Washington Post reported.