North Korea's leader Kim Jong Un speaks at the Capella Hotel on Sentosa island in Singapore on June 12, 2018.

North Korea is working to ensure its nuclear and ballistic missile capabilities cannot be destroyed by military strikes, U.N. monitors said ahead of a meeting between U.S. and North Korean officials to prepare a second denuclearization summit.

The U.S. special envoy for North Korea, Stephen Biegun, will meet his North Korean counterpart on Wednesday in Pyongyang to prepare for a summit later this month between President Donald Trump and North Korean leader Kim Jong Un, the U.S. State Department said on Monday.

Biegun has said he hoped the meeting with new North Korean counterpart Kim Hyok Chol would map out "a set of concrete deliverables" for the summit between Trump and Kim Jong Un.

Biegun, who held talks with South Korean officials in Seoul on Sunday and Monday, said he would be aiming for "a roadmap of negotiations and declarations going forward, and a shared understanding of the desired outcomes of our joint efforts."

South Korean officials said they and the United States could be looking at a compromise that could expedite North Korea's denuclearization - the dismantling of the North's main Yongbyon nuclear complex, which could be reciprocated by

U.S. measures including formally ending the 1950-53 Korean War and setting up a liaison office.

But U.N. sanctions monitors said in a confidential report, submitted to a 15-member U.N. Security Council sanctions committee and seen by Reuters on Monday, that they had "found evidence of a consistent trend on the part of the

DPRK to disperse its assembly, storage and testing locations", using the abbreviation for North Korea's official name, the Democratic People's Republic of Korea.

The North Korean mission to the United Nations did not immediately respond to a request for comment on the report, which was submitted to Security Council members on Friday.

The first summit between Trump and Kim Jong Un last June in Singapore yielded a vague commitment by Kim to work toward the denuclearization of the Korean peninsula, where U.S. troops have been stationed since the 1950-53 Korean War.

The Vietnamese resort town of Danang is seen as the most likely location for the next summit.

Trump last Thursday hailed "tremendous progress" in his dealings with North Korea, but the view in the United States is that it has yet to take concrete steps to give up its nuclear weapons program.