Three North Korean officials, including the top envoy involved in talks with the United States, are booked on a flight to Washington, South Korean media reported on Wednesday, suggesting possible movement toward a second summit between Donald Trump and the North Korean leader, Kim Jong-un.

US and South Korean media quoted sources as saying that the US secretary of state, Mike Pompeo, and senior North Korean official Kim Yong-chol were expected to meet on Friday in the US capital to discuss the summit.

The White House and the US state department declined to confirm the reports, perhaps wary of another last-minute cancellation. Pompeo planned to meet his counterpart to discuss a second summit last November, but the state department had to postpone the meeting the day after announcing it.

While Trump has been eager to hold a second summit with Kim, on Wednesday the US vice-president, Mike Pence, acknowledged that efforts to persuade North Korea to give up its nuclear arsenal had not made headway.

“While the president is promising dialogue with Chairman Kim, we still await concrete steps by North Korea to dismantle the nuclear weapons that threaten our people and our allies in the region,” Pence said in an address at the state department.

The South Korean news agency Yonhap, citing an unidentified Chinese airport official, said Kim Yong-chol, along with North Korea’s vice foreign minister, Choe Son-hui, and a third official, would leave Beijing on Thursday for Washington.

Kim Yong-chol was last in Washington in June, when he delivered a letter from Kim Jong-un to Trump that opened the way for an unprecedented meeting between leaders of the two countries in Singapore on 12 June 2018.

CNN quoted a source familiar with US-North Korea talks as saying that Kim Yong-chol would be carrying a new letter from Kim Jong-un to Trump in Washington.

If he stays overnight in Washington, Kim Yong-chol would be the first top North Korean to do so since the late vice-marshal Jo Myong-rok did so ahead of talks with then president Bill Clinton and secretary of state Madeleine Albright in 2000.

In Singapore, the North Korean leader pledged to work toward denuclearization of the Korean peninsula, but there has been little significant progress since.

Contact was resumed after Kim Jong-un delivered a New Year speech in which he said he was willing to meet Trump “at any time”, South Korea’s ambassador to the US, Cho Yoon-je, told reporters last week.

The two sides would seek “interim” measures to revitalize the denuclearization process, South Korea officials told Reuters, but North Korea has demanded a lifting of US sanctions and dismissed US demands it declare all its nuclear weapons and facilities.

In spite of Pence’s remarks, a White House official referred to past comments by Trump that “a lot of positive things are happening” with North Korea.

“He and Chairman Kim have established a good relationship, and conversations between the United States and North Korea continue,” said the official.

“We are working to make progress on our goal of achieving the final, fully verified denuclearization of North Korea, and the president looks forward to meeting Chairman Kim again at their second summit at a place and time yet to be determined.“