North Korea on Monday said it was ready to allow an international group of inspectors into the country’s clandestine nuclear and missile sites, a move that could be seen as more evidence in Washington and Pyongyang’s thawing relationship.

Mike Pompeo, the U.S. secretary of state, made the announcement after a Sunday meeting with North Korean leader Kim Jong Un. The meeting was apparently productive, and they even discussed another summit between Kim and President Trump, Reuters reported.

Pompeo identified Punggye-ri as one of the testing sites mentioned in their conversations. The U.S.’s top diplomat retweeted Trump’s tweet touting a “good meeting” in Pyongyang.

"We continue to make progress on agreements made at Singapore Summit," Pompeo tweeted. Trump met with Kim in Singapore in June and – at the time – announced that the two countries are set to "start a new history."

The tone of the meeting was cordial. Pompeo was hit by North Korean officials a few months ago as having a “gangster-like demand for denuclearization.”

Trump also called off a meeting with Pompeo in August, due to a lag in the negotiations.

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The Washington Post reported that Pompeo met with Kim for about two hours and had lunch. Kim told Pompeo as they sat down, “It’s a very nice day that promises a good future for both countries.”