"I don't have anything to add on the sequence of events in North Korea. But I'm very hopeful we will have senior-level meetings before too long," the top US diplomat told reporters after a Senate hearing on US policy in the Middle East.

The US and North Korea have been trying to flesh out a denuclearization agreement reached between Trump and Kim at their historic Singapore summit in June. Kim committed then to work toward "complete" denuclearization in exchange for security guarantees from the US

Pompeo has led the negotiations with Pyongyang, including through four trips to the North Korean capital this year.

But progress has been slow as the US insists the North first achieve "final and fully verified" denuclearization, while the North demands sanctions relief and a formal end to the 1950-53 Korean War.

Trump has said he still expects to hold a second summit with Kim early next year.

"We are in frequent contact with North Korean officials. That's not changed," State Department spokeswoman Heather Nauert told reporters Tuesday. "We have our special representative, Steve Biegun, who is leading those conversations. We have those types of conversations, meetings at various levels from the secretary level to Steve Biegun's level to the working level, so those conversations continue."

Earlier, some news outlets reported that the US had offered to reschedule the Pompeo-Kim meeting for Wednesday at the latest, before the secretary accompanies US President Donald Trump to a Group of 20 summit in Argentina this weekend.

That offer apparently failed to materialize. (Yonhap)