South Korea's top nuclear envoy headed to the US on Wednesday for consultations on North Korea ahead of back-to-back summit talks among the countries that will likely redefine regional security conditions.

The trip by Lee Do-hoon, representative for Korean Peninsula peace and security affairs at the foreign ministry, is part of hectic diplomacy on Pyongyang's nuclear program and efforts to bring a permanent peace to the peninsula.

While in Washington DC he plans to meet key players in the Donald Trump administration handling Korea affairs before returning to Seoul on the weekend. They include Susan Thornton, acting US assistant secretary of state for East Asian and Pacific affairs, and Matthew Pottinger, senior director for Asian affairs at the National Security Council, according to ministry officials.

High on the agenda are the denuclearization of Korea and the establishment of a peace regime.

The two sides will also discuss coordination on the implementation of the April 27 inter-Korean summit deal known as the Panmunjom Declaration.

Trump is scheduled to host a summit with South Korean President Moon Jae-in at the White House on May 22, followed by a meeting with the North's leader Kim Jong-un.

The date and venue for the Kim-Trump talks have yet to be announced.

US Secretary of State Mike Pompeo is apparently on a visit to Pyongyang for last-minute consultations on the details of the summit. He may also strike an agreement on the release of three American citizens held in the communist nation.

Earlier this week, the North's leader held surprise talks with Chinese President Xi Jinping in Dalian, a northeastern Chinese city, the second meeting between them in about 40 days.(Yonhap)