The United States plans to send its special envoy for North Korean human rights to Seoul later this month, a diplomatic source said Thursday, raising expectations that he may also travel to Pyongyang on a mission to negotiate the release of a jailed American man.

"Amb. Robert King is scheduled to visit South Korea in the week starting on Nov. 18," the source told Yonhap News Agency on the condition of anonymity.

The State Department will soon make the announcement of his trip, which may also include stops in Beijing and Tokyo, added the source.

It would be King's second visit to the region in less than three months.

In late August, he made a visit to Northeast Asia during which the U.S. government unexpectedly announced his plan for a trip to Pyongyang aimed at securing the freedom of Kenneth Bae.

But North Korea abruptly canceled the invitation, further damaging its credibility among U.S. officials.

Observers say North Korea, which is largely on a charm offensive, may release him on the occasion of Thanksgiving, which falls on Nov. 28 this year.

If so, it may help China's efforts to reconvene the six-way nuclear talks, they point out.

The source, however, said it remains unclear whether King will get an invitation from North Korea this time.

Bae, a Christian missionary, was arrested in North Korea a year ago after entering the nation with a group of tourists. The North later announced that its highest court sentenced him to 15 years of compulsory labor for committing an unspecified crime against the state.

The State Department reaffirmed its willingness to dispatch King to the North should it invite him again.

"If the DPRK (North Korea) renews its invitation, Special Envoy for North Korean Human Rights Amb. Robert King is prepared to travel to the DPRK on a humanitarian mission focused on securing the release of Mr. Bae," the department's deputy spokeswoman Marie Harf told Yonhap News Agency.

Washington has urged Pyongyang to grant Bae special amnesty and immediate release on humanitarian grounds.

Bae's mother, a resident of Seattle, visited Pyongyang last month to meet with her son.

"We are in regular contact with the Bae family and helped facilitate communications with our protecting power, the government of Sweden, for Mrs. Bae's private trip," Harf said.

The Swedish Embassy in Pyongyang serves as the protecting power for U.S. citizens there, as the U.S. has no formal diplomatic ties with the communist nation.

Human rights groups have also called for Bae's release.

International Christian Concern pointed out that Bae is the longest known American detainee in North Korea since the 1950-53 Korean War. (Yonhap News)