"We have a shared goal here, which is to bring an end to 70 years of war and hostilities on the Korean Peninsula. And the primary requirement for us to get to the end point is to achieve final, fully, verified denuclearization of North Korea," Biegun said at the outset of the talks.

He added, "I am absolutely confident this is within reach."

Lee pointed out the denuclearization process is "at a critical juncture" and said what's important is to maintain close cooperation on the North Korea issue.

"We need to meet up as often as possible to make sure there is no daylight whatsoever between our two allies," he added.

Biegun arrived in Seoul on Sunday for a three-day stay, his fourth visit here as Washington's point man on Pyongyang.

It came less than a week after he sat down with Lee in Washington.

He had a brief meeting with Foreign Minister Kang Kyung-wha as well.

The envoy is scheduled to meet Unification Minister Cho Myoung-gyon, who's in charge of Seoul's ties with Pyongyang, and presidential officials on Tuesday.

The liberal Moon Jae-in government has been struggling to convince the people that it's in lockstep with the US in engaging the North.

US officials, however, are reportedly displeased with Seoul's push for speedy inter-Korean economic projects despite there being no further progress in efforts to rid the North of its nuclear arsenal.

During a roundtable meeting with a group of South Korean reporters visiting the US capital last week, Bruce Klingner, senior research fellow at the Heritage Foundation, said US.

officials are actually upset about the Moon administration's pursuit of an easing of sanctions despite their outward talk of close partnerships.

Secretary of State Mike Pompeo met with the North's leader Kim Jong-un in early October, but there have been no follow-up negotiations yet.

It remains unconfirmed whether Biegun plans to have talks with the North's Vice Foreign Minister Choe Son-hui during his ongoing visit to Korea.

He sought to meet her in Vienna but Choe did not respond to such overtures, according to an informed source.

Meanwhile, another North Korean vice foreign minister, Sin Hong-chol, is on a visit to Moscow for consultations with Russian officials including the chief nuclear negotiator, Igor Morgulov. (Yonhap)