One of North Korea’s top negotiators is on his way to Washington to meet US officials ahead of a possible second summit between Kim Jong-un and US President Donald Trump.
South Korean reports say that Kim Yong-chol, flying from Beijing, is carrying another letter from Mr Kim to Mr Trump.
He is expected to meet US Secretary of State Mike Pompeo on Friday. Speculation is mounting that the second summit could be held in Vietnam.
The North Korean leader is scheduled to travel to the communist-run country for an “official state visit” sometime in February, Reuters news agency is reporting, citing unnamed sources.
Little progress has been made on North Korean de-nuclearisation since a historic meeting in Singapore last June between Mr Kim and Mr Trump.
But there has recently been a flurry of diplomatic activity. Mr Kim visited China earlier this month for talks with President Xi Jinping, as he did before the Singapore summit.
Meanwhile another senior North Korean official, vice-foreign minister Choe Son-hui, is heading to Sweden, where she could meet Washington’s special representative for Pyongyang Stephen Biegun, reports say.