WASHINGTON/SEOUL, U.S. Secretary of State Mike Pompeo said Friday he's visiting North Korea this week to maintain the momentum of a June 12 Singapore summit deal on improving bilateral ties and denuclearizing the communist nation.

"On this trip I'm seeking to fill in some details on those commitments and continue the momentum toward implementation of what the two leaders promised each other and the world," he was quoted as telling pool reporters during a brief stopover in Japan.

He was on his way to Pyongyang for his third visit as Washington's top diplomat and key player in the Donald Trump administration's engagement with the North.

He plans to have a day and a half of meetings with the North's officials to follow up on Trump's summit agreement with the North's leader Kim Jong-un.

It would be his first overnight stay in the North.

Key issues include securing a declaration of all of North Korea's nuclear arsenal, a verification regime for dismantlement and a timeline for denuclearization.

North Korea could also deliver the remains of some American soldiers killed in the 1950-53 Korean War.

Shortly after his North Korea visit, Pompeo will fly to Tokyo for a trilateral meeting with his South Korean and Japanese counterparts -- Kang Kyung-wha and Taro Kono - this weekend.

"Looking forward to continuing our work toward the final, fully verified denuclearization of #DPRK, as agreed to by Chairman Kim," Pompeo also tweeted en route, using the acronym for North Korea's formal name, the Democratic People's Republic of Korea.

"Good to have the press along for the trip," he added. Six reporters are accompanying him.

Meanwhile, U.S. National Security Adviser John Bolton said Sunday that he expects Pompeo to discuss with the North Koreans a plan to dismantle the nuclear weapons and ballistic missile programs in a year.

State Department spokeswoman Heather Nauert on Tuesday declined to provide a timeline, saying the secretary will be going into the meetings "eyes wide open, with a very clear view of these conversations."

She also denied that the U.S. has eased its demand for "complete, verifiable and irreversible denuclearization," speculation that emerged after the State Department started defining its goal as the "final, fully verified denuclearization" instead.

"Nothing could be further from the truth. Our policy toward North Korea has not changed," Reuters quoted Nauert as telling reporters en route to Pyongyang. "We are committed to a denuclearized North Korea and Secretary Pompeo looks forward to continuing his consultations with North Korean leaders to follow up on the commitments made at the Singapore summit."

News reports over the weekend cited U.S. intelligence sources as questioning the North's commitment to abandoning its nuclear arsenal.

Many of them pointed to findings that indicate a build-up of the regime's nuclear-related facilities. They also accused Pyongyang of trying to deceive Washington in order to extract concessions without ever giving up its nuclear program.

Source: Yonhap News Agency