* US Secretary of State Pompeo on third trip to Pyongyang
* List of initial nuclear sites high on agenda
* Secure remains of 200 U.S. soldiers from Korean War
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By Hyonhee Shin and John Walcott
SEOUL/WASHINGTON, July 6 (Reuters) - U.S. Secretary of State Mike Pompeo will visit North Korea on Friday, seeking to secure the remains of some 200 U.S. troops missing from the Korean War and initial agreement on the North's nuclear facilities to be declared.
Pompeo is expected to land in Pyongyang at around noon (0300 GMT) after a brief stopover in Japan, according to a pool report by reporters travelling with him.
The secretary will spend a day and a half in North Korea until Saturday on his third trip to Pyongyang. It will begin with lunch with Kim Yong Chol, a senior North Korean official who played a central role together with Pompeo in arranging last month's unprecedented summit between President Donald Trump and North Korean leader Kim Jong Un in Singapore.
At the summit, Kim made a broad commitment to "work toward denuclearisation," but fell short of details on how or when he would dismantle the nuclear programmes.
"The President told me he believes that Chairman Kim sees a different, brighter future for the people of North Korea. We both hope that's true," Pompeo said on Twitter after a phone call with Trump in the air.
He is seeking to "fill in" some details on those commitments and maintain the momentum toward implementation of the agreement from the summit, Pompeo said, according to the pool report.
Pompeo would try to agree on at least an initial list of nuclear sites and inventory that can be checked against the available intelligence, U.S. intelligence officials told Reuters.
Also high on the agenda is a return of the remains of 200 U.S. soldiers missing from the 1950-53 conflict, which Trump said had been sent back, though there was no official confirmation from military authorities.
Both are considered essential tests of whether Kim is serious about negotiations, which so far North Korean officials have yet to demonstrate in working-level talks, the intelligence officials said.
"If they're serious, then we can get down to the business of defining the terms of final denuclearisation," said one official.
But the U.S. ability to verify the accuracy of any list from Pyongyang is limited due to the lack of a "high confidence" accounting of the North's nuclear arsenal, such as the number of warheads and uranium enrichment facilities, especially if they are not operational, they said.
Identifying any and all U.S. troops who might be returned from North Korea may also be challenging.