The U.S. is ultimately pursuing a “peaceful pressure” campaign aimed at denuclearizing North Korea, said Secretary of State Rex Tillerson in an interview on Sunday.

Tillerson was one of several U.S. officials who hit the Sunday talk shows to comment on the current crisis in the Korean Peninsula. U.S. Last week, the United Nations upped sanctions against Pyongyang, which responded by launching another missile over Japan, after threatening to sink that country into the sea and to reduce the U.S. to ”ashes and darkness.”

The U.S. is working toward getting North Korea to engage in “constructive, productive, dialogue,” Tillerson said, adding that if diplomatic efforts fail, then the only option will be a military one. But his comment that the U.S. wanted a peaceful end to the crisis was serving to help prop up global stocks on Monday, with stock futures pointing to fresh record highs.

“ ‘So all of this is backed up by a very strong and resolute military option. But to be clear, we seek a peaceful solution to this.’ ” — — Rex Tillerson, U.S. Secretary of State

He also said the U.S. wants China to help step up pressure on North Korea by cutting off its vital oil supply, while Russia can clamp down on foreign laborers from the isolated nation.

But a slightly tougher tone emerged in comments from Nikki Haley, U.S. ambassador to the United Nations, who said President Donald Trump’s “fire and fury” comment last month wasn’t just an empty threat.

“If North Korea keeps on with this reckless behavior, if the United States has to defend itself or defend its allies in any way, North Korea will be destroyed,” Haley said on CNN’s “State of the Union” Sunday. “And we all know that, and none of us want that.”

Meanwhile, White House National Security Adviser H.R. McMaster said U.S. policy remains that North Korea must denuclearize and that “all options are on the table,” speaking the same day on ABC’s “This Week.”

Trump himself poked fun at North Korea’s leader, Kim Jong Un, in a tweet Sunday, in which he suggested the country was starting to feel some heat from international sanctions.

Passing comment on another Communist country, Tillerson said the U.S. is evaluating a closure of its embassy in Cuba, after a suspected series of acoustic attacks that left diplomats ill.