WASHINGTON (Reuters) - White House national security adviser John Bolton on Tuesday said North Korea has not taken the necessary steps to denuclearize despite an agreement between Pyongyang’s leader Kim Jong Un and U.S. President Donald Trump in June.

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Bolton, in an interview on Fox News, said U.S. Secretary of State Mike Pompeo was prepared to return to North Korea for another meeting with Kim.

“What we really need is not more rhetoric,” Bolton said. “What we need is performance from North Korea on denuclearization.”

Kim and Trump promised to work to end North Korea’s weapons programs at their summit in Singapore, but the two countries have been struggling to reach a detailed accord to meet that goal.

Pyongyang’s state media has highlighted it has made goodwill gestures, such as a moratorium on nuclear and missile tests, the dismantling of a nuclear site, and the return of the remains of U.S. soldiers killed in the 1950-53 Korean War.

It has urged Washington to take reciprocal steps including officially declaring an end to the war and dropping sanctions.

Satellite images from last Friday indicate North Korea has carried out additional activities to dismantle a key missile launch facility, the Washington-based 38 North think-tank said on Tuesday.

Photos from last Friday showed recent work at the Sohae station to tear down an engine test stand and remove fuel and oxidizer tanks from bunkers, though the possibility can’t be ruled out that the North might be trying to modify the stand for other purposes.

Bolton said the United States has lived up to the Singapore declaration that followed the June 12 summit.

“It’s just North Korea that has not taken the steps we feel are necessary to denuclearize,” Bolton said.

He said the relaxation of any sanctions was not under consideration.

Asked about the possibility of additional meetings, Bolton said Trump in a recent letter to Kim proposed sending Pompeo back to North Korea, and that Trump was ready to meet with Kim any time. The letter was handed to North Korean Foreign Minister Ri Yong Ho during the weekend.

North Korea’s nuclear weapons program has caused international tension for decades and the rhetoric and threats from Kim and Trump had been especially hostile before their June meeting.