Nikki Haley, the United States ambassador to the United Nations, clarified on Sunday that President Donald Trump's "fire and fury" comment last month about North Korea's nuclear program was not an empty threat.

Speaking to CNN, Haley stressed that Defense Secretary James Mattis has an array of options to destroy North Korea.

If the U.S. exhausts diplomatic options on North Korea, the U.S. military would "take care of it," Haley said.

"We wanted to be responsible and go through all diplomatic means to get their attention first," Haley said. "If that doesn't work, General Mattis will take care of it."

"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," she stressed. "And we all know that, and none of us want that."

Trump recently warned Pyongyang it faced "fire and fury like the world has never seen" if it continued to threaten the United States with its missile and nuclear programs.

North Korea responded by conducting its sixth and largest nuclear test, and later warning it would send “more gift packages” to the U.S. if it continues to pressure Pyongyang.

The United Nations Security Council adopted a new round of sanctions on North Korea last Monday in response to its latest test.

Trump called the move "another very small step," but Haley talked up the significance of the agreement and went on to say it was near the limit of what the U.S. could accomplish through the UN.

"We have pretty much exhausted all the things that we could do at the Security Council at this point," she said.

Her comments come after White House national security adviser H.R. McMaster said on Friday there is a military option for handling North Korea's missile and nuclear testing.

McMaster stressed that the administration again wants new sanctions against North Korea to work. At the same time, he warned that the regime has stepped up testing and that means that "we're out of time."

"We've been kicking the can down the road, and we're out of road," he said. "So for those who have said and commenting about the lack of a military option, there is a military option."