FILE PHOTO: A combination photo shows Mike Pompeo (L) in Washington, DPRK top leader Kim Jong Un (C) in Pyongyang and U.S. President Donald Trump (R), in Palm Beach, Florida, U.S., respectively from Reuters files.

WASHINGTON, May 9 (Xinhua) -- U.S. Secretary of State Mike Pompeo said Wednesday that the time and venue of the meeting between the Democratic People's Republic of Korea (DPRK)'s top leader Kim Jong Un and U.S. President Donald Trump have been "locked in."

Pompeo told reporters aboard his plane before arriving at Japan's Yokota Air Base for a stopover.

The U.S. top diplomat said that he talked with Kim in "a good and lengthy conversation" in preparation for the latter's possible meeting with Trump, adding Washington will announce them "in the next handful of days."

Trump said on the same day that the location of his meeting with Kim will not be at the Demilitarized Zone (DMZ) separating the DPRK and South Korea, and the time and place for the meeting will be announced in three days.

"We had a chance to talk substantively about what we intend to be on the agenda, and also how we're going to begin to coordinate in the days ahead between now and the summit," Pompeo noted.

"Both sides are confident that we will set the conditions for a successful meeting between the two leaders."

"There were no moments where I felt like we were going to be anything but successful in the day," he said, noting the meeting "worth the time and effort, and I think very productive."

Speaking of the three freed U.S. citizens that came with him, Pompeo said "the doctors are with them now, but all indications are at this point that their health is as good as could be..."

He said the United States will have a "more complete readout of their complete conditions" in the next couple of hours.

Explaining the reason for the sudden release of them, Pompeo said "Kim is trying to set good conditions for the summit" with Trump.

"But there's still a lot of work to do to achieve our ultimate goal," he said, referring to what the United States has called a complete, verifiable and irreversible denuclearization of the Korean Peninsula.

Trump, for his part, also praised Kim Jong Un for the release of the three U.S. citizens who were accused of trying to undermine the DPRK government.

Trump said that he and Vice President Mike Pence will be at Andrews Air Force Base to meet them at 2:00 a.m. EDT (0600 GMT) Thursday.

The White House earlier on Wednesday confirmed the release of three U.S. citizens detained in the DPRK, saying Trump appreciates the release and views it as "a positive gesture of goodwill."