US Special Representative for North Korea Stephen Biegun returned to Washington on Friday after a dayslong trip to South Korea, Japan and China, suggesting he remains open to meeting with North Korean officials to discuss the country's denuclearization.

Biegun arrived at Dulles International Airport on a flight from Beijing after what would have been an impromptu meeting with the North Koreans apparently did not materialize.

The special representative traveled to the region as tensions have risen over North Korea's threats to resume nuclear or long-range missile tests unless the United States offers concessions to break their deadlock in denuclearization talks before the end of the year.

"You heard what I said in South Korea and those remarks stand," Biegun said when asked whether he met the North Korean delegation in Beijing.

While in Seoul earlier this week, the special representative made a public offer to meet with the North Koreans, saying it was time for the two sides to "do our jobs" and work toward an agreement.

US President Donald Trump and North Korean leader Kim Jong-un agreed during their first summit in Singapore in June 2018 to pursue complete denuclearization of the Korean Peninsula in exchange for US security guarantees.

But negotiations to implement the deal have faltered amid wide gaps over how to match the North's denuclearization steps with US concessions, including sanctions relief.

Biegun was originally scheduled to visit South Korea and Japan this week to meet with officials of those two countries on the way forward with North Korea.

The State Department later announced that he would also visit China, prompting speculation the US delegation was extending its stay in the region to allow more time for a meeting with the North Koreans.

The last time the two sides met was in Sweden in October. Those talks ended with the North accusing the US side of having come "empty-handed."

Pyongyang has warned of an unwelcome "Christmas gift" unless Washington takes steps to salvage the negotiations. A top US Air Force general said earlier this week he expects the "gift" to be a long-range missile test.

Peppered with questions from reporters, Biegun answered, "Here's my message, and it's to all of you: Have a merry Christmas."

He also thanked a reporter who called him "Mr. Secretary," a reference to his Senate confirmation Thursday to be the deputy secretary of state, saying it was "the first time in the US I've been called that." (Yonhap)