Robert King, the US special envoy for North Korean rights, will arrive in Pyongyang on Friday, the state department said.
He will request a pardon and amnesty for Kenneth Bae, 45, on humanitarian grounds, it said.
Kenneth Bae, a Korean-American, was given 15 years’ hard labour in May for trying to overthrow the North Korean government.
His family say he is seriously ill and has been moved from a labour camp to a hospital. They say he has diabetes and an enlarged heart.
“We remain deeply concerned about the health and welfare of Kenneth Bae,” a White House statement said.
“We urge the government of North Korea to grant special clemency to Mr. Bae immediately and allow him to return home with Ambassador King.”
Kenneth Bae (known in North Korea as Pae Jun-ho) was arrested in November 2012 as he entered the north-eastern port city of Rason, a special economic zone near North Korea’s border with China.
He has been described as both a tour operator and Christian missionary.
North Korea said he used his tourism business to form groups to overthrow the government.
Kenneth Bae’s trial and conviction came at a time of high tension between the US and North Korea, in the wake of the communist state’s third nuclear test. It also came as the US and South Korea conducted annual large-scale military exercises, which angered Pyongyang.
North Korea has arrested several US citizens in recent years, including journalists and Christians accused of proselytising.
They were released after visits to Pyongyang by high-profile officials, including former presidents Bill Clinton and Jimmy Carter.
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