The United States and North Korea do not appear to have had behind-the-scenes discussions since their working-level denuclearization negotiations ended without an agreement in Sweden earlier this month, South Korea's ambassador to the US said Thursday.

Lee Soo-hyuck made the remark after meeting with US Special Representative for North Korea Stephen Biegun, Washington's chief envoy to the talks with Pyongyang, for the first time since taking up his post last week.

Lee also said Biegun expressed his intent to keep his North Korea portfolio regardless of any change in his "status."

Hours later, US President Donald Trump nominated Biegun as deputy secretary of state to replace John Sullivan, who has been picked to be Washington's next ambassador to Russia.

"I still believe it isn't appropriate to despair or describe (the Stockholm talks) as having broken down," the ambassador said.

"From what I've heard from South Korean and US officials, I don't get the impression that it's over."

Asked if he believes the US and North Korea are currently in discussions behind the scenes, he said, "Well, I didn't (get the impression) that that was happening."

On the possibility the two sides could resume working-level negotiations as early as November, he said, "I didn't think there was anything on which to forejudge."

The ambassador refused to share details of his meeting with Biegun, except to say that the special representative explained the current situation with North Korea, as well as how the Oct. 5 Stockholm talks proceeded and ended.

There was no discussion of the North's short-range projectile launches that took place early Thursday, he added. (Yonhap)