U.S. President Donald Trump will not hold a meeting with North Korean leader Kim Jong Un as scheduled by early June unless it advances the interests of the United States, Japan and the international community, the U.S. ambassador to Japan said Wednesday.

"If he feels that this meeting is not going to be productive and it's not going to advance U.S., Japan and international interests, he'll not go," William Hagerty told reporters after a two-day meeting between Trump and Japanese Prime Minister Shinzo Abe in Palm Beach, Florida.

"If he feels that he can, he'll attend," said Hagerty of what would be the first-ever U.S.-North Korea summit.

Hagerty, who attended the Abe-Trump meeting at the U.S. leader's Mar-a-Lago estate, made the remarks after Trump suggested in a post-summit news conference with Abe that he will not meet with Kim if he does not think the meeting will be successful.

Hagerty said a Trump-Kim meeting would address the complete, verifiable and irreversible denuclearization of North Korea, the North's missiles, chemical and biological weapons, as well as three American citizens being detained in North Korea and Pyongyang's abduction of Japanese nationals in the 1970s and 1980s.

If Kim attempts to buy time through his direct engagement with Trump, the United States will step up sanctions and pressure on North Korea, the envoy said.

"This is all aimed at making certain that we move toward having a meeting that is constructive and moving our agenda forward," he said.

"If we have a sense that that is not the case, the president is not going to waste his time, and frankly (he is) not interested in allowing more time to pass and we will continue to increase pressure, ratchet up diplomatic sanctions, increase the pressure on the North Korean regime."

Earlier Wednesday, Trump said his Secretary of State-nominee Mike Pompeo got along with Kim "really well" during his recent secret trip to the North, apparently to lay the groundwork for a Trump-Kim meeting.

Pompeo, currently director of the Central Intelligence Agency, "had a great meeting with Kim Jong Un, and got along with him really well, really great," Trump said.

The U.S. leader tweeted that Pompeo met with Kim last week. "Denuclearization will be a great thing for World, but also for North Korea!" he wrote.

Trump said details of the planned meeting with Kim "are being worked out now."

On Tuesday, Trump said he is looking at five potential sites for the unprecedented meeting.

None of the five places under consideration is in the United States, he said.

Washington and Pyongyang have no diplomatic relations.