Asked if he had contacted the North Korean side while in Asia, Biegun told reporters at the airport, "No comment this time." He also refused to answer a question about the purpose of his trip to China.

Commenting on his weeklong trip to Asia, South Korea's presidential office Cheong Wa Dae said what matters is continued efforts to keep up the momentum of dialogue with the North.

"In accordance with his schedule, Deputy Secretary Biegun is returning home today," a senior Cheong Wa Dae official told reporters in Seoul.

"The key point now is that we are making all-out efforts to maintain dialogue momentum between North Korea and the US," he added.

His high-profile Asia swing came as the North has been threatening to take a "new way" if the US does not make concessions for progress in the stalemated negotiations before Pyongyang's year-end deadline.

The recalcitrant regime has sent out cryptic signals that it could engage in provocative acts should the deadline be missed. It carried out two apparent rocket engine tests at its west coast satellite launch site this month, sparking worries that it could fire off a long-range rocket under the guise of peaceful space development activity.

Biegun was confirmed as deputy secretary of state during his unscheduled two-day trip to China. Before the trip, he visited South Korea and Japan this week.

His trip to China appeared aimed at demanding Beijing exert its influence to bring Pyongyang back to dialogue.

Biegun might have also used the trip to urge China not to break ranks and weaken the global sanctions regime against the North, as Beijing and Moscow proposed a draft UN resolution this week to call for partial sanctions relief.

On Thursday, Biegun met Vice Foreign Minister Luo Zhaohui to discuss ways to make progress in the efforts to denuclearize the North.

Luo reportedly proposed that the US take conciliatory gestures, such as partial sanctions relief, to explore a diplomatic and political solution to the North's nuclear quandary. He also appeared to have renewed Beijing's call for a phased, simultaneous denuclearization process rather than a comprehensive, big-deal approach.

In a press release following the talks between Biegun and Luo, China's foreign ministry said that it hopes the US and the North resume dialogue as soon as possible to "actively build trust and effectively handle their dispute."

Biegun appeared to have used the talks to stress the importance of sustaining sanctions pressure on the North, which the US sees as a key lever to bring the North back to the dialogue table and keep it on the denuclearization track.

The US and the North last held working-level talks in Sweden in October. But the meeting yielded little progress, with the North accusing the US of having come to the negotiating table "empty-handed."

Since then, Pyongyang has toughened its demands, telling the US to remove "all obstacles" that threaten the security of the North and hamper its development. The demands are seen as calls for sanctions relief and security assurances. (Yonhap)