"First, President Trump will arrive in Seoul tomorrow and we can work together and get prepared to help our leaders ensure the success of the summit," Lee said at the start of his talks with Biegun.

"Second, we have witnessed a lot of diplomatic interactions and activities on and around the Korean Peninsula recently, and we can discuss ways and means how to translate them into substantive progress on denuclearization and peace on the Korean Peninsula," he added.

Biegun said in turn, "I look forward our discussions."

Later in the day, Biegun will pay a visit to Unification Minister Kim Yeon-chul possibly to discuss inter-Korean ties and Seoul's recent provision of humanitarian support to the impoverished neighbor via international aid agencies.

Trump will begin his two-day trip to Seoul on Saturday after his attendance at the Group of 20 summit in Osaka, Japan. He will hold a summit with South Korean President Moon Jae-in on Sunday to explore ways to address the deadlock in nuclear talks with the North.

Negotiations between Washington and Pyongyang have been at an impasse since the no-deal summit between Trump and North Korean leader Kim Jong-un in Hanoi in February.

In recent weeks, Trump and Kim exchanged personal letters, which bolstered expectations that the United States and the North could resume their working-level talks to bridge differences and pave the way for a possible third summit.

A key sticking point between the two sides is the extent of Pyongyang's denuclearization in return for Washington's sanctions relief.

During the Hanoi summit, Kim offered to dismantle the mainstay Yongbyon nuclear complex, but Trump wanted more than the complex, which the US sees as only a part of the North's sprawling nuclear program.

During an event at the Atlantic Council think tank earlier this month, Biegun emphasized that the "door is wide open" to negotiations with the North and without preconditions.

He also noted that both sides understand the need for a "flexible approach" -- remarks that some observers said insinuated the US' willingness to ease its hard-line stance.

Speculation has persisted that Biegun might travel to the inter-Korean border truce village of Panmunjom to meet North Korean officials. But on Thursday, an official at Seoul's foreign ministry hinted that he might not have sufficient time to visit Panmunjom. (Yonhap)