His trip came as the conclusion of a combined South Korea-US military exercise raised the prospects for the resumption of working-level nuclear negotiations between Washington and Pyongyang.

The communist regime had berated the exercise as a rehearsal for invasion, shunning negotiations with the United States, firing a fusillade of short-range projectiles into the East Sea and sharpening its rhetoric against the South.

Biegun and Lee were expected to coordinate the allies' positions and strategies over how to make progress once negotiations with the North are relaunched.

Washington and Pyongyang were expected to resume the working-level talks last month based on an agreement between US President Donald Trump and North Korean leader Kim Jong-un during their impromptu talks at the inter-Korean border on June 30.

But the talks have not been held amid tensions over the combined military exercise between Seoul and Washington.

US Secretary of State Mike Pompeo expressed hope Tuesday that the North will return to negotiations to dismantle its nuclear weapons program.

"We hope Chairman Kim will come to the table and get a better outcome. It will be better for the North Korean people. It will be better for the world," he said in an interview with CBS.

Trump has tweeted that in a recent letter to him, the North Korean leader expressed his desire to relaunch the talks with the US as soon as the allied exercise ends.

Biegun's visit to Seoul has spawned speculation that during his stay here, he could meet North Koreans at the inter-Korean truce village of Panmunjom and resume much-awaited nuclear negotiations.

On Thursday, Biegun reportedly plans to meet Kim Hyun-chong, a deputy director of the National Security Office, at the presidential office Cheong Wa Dae. (Yonhap)