An alleged U.S. Army deserter who lived in North Korea for 39 years appears set to travel to Tokyo for medical treatment as soon as this weekend, but U.S. officials on Thursday said they reserved the right to request his custody, even though that might not occur immediately.

Nonetheless, Japanese officials were making plans to bring Charles Robert Jenkins, 64, to Japan from Jakarta, Indonesia.

Prime Minister Junichiro Koizumi has championed Jenkins's case and expressed hope that Jenkins would be allowed to live in Japan with his wife, Hitomi Soga, and two daughters.

"I am indeed worried about his medical condition and I am making efforts at enabling the family of Ms. Soga to live together in Japan," Koizumi said.

"In principle," he told reporters late Wednesday, "I hope to explore a solution that would satisfy both countries based on the strong relationship of trust between Japan and the United States."

Jenkins had flown from North Korea to Indonesia with his two daughters on July 9 for a reunion with Soga. Soga was one of five Japanese abducted by North Korean agents during the 1970s and 1980s and returned to Tokyo in October 2002 after a landmark summit in Pyongyang between Koizumi and the North Korean leader, Kim Jong Il.

U.S. authorities charge that Jenkins, a North Carolina native, crossed into North Korea while on patrol in South Korea in 1965. Since then, he has starred in North Korean anti-American propaganda films, playing the role of a CIA agent gone bad. His family in the United States maintains Jenkins was kidnapped and brainwashed.

According to Howard H. Baker Jr., the U.S. ambassador to Japan, the issue has become "a matter of extraordinary importance" between the United States and Japan, and is being dealt with on a "presidential level." Koizumi, President Bush's closest ally in Asia, who resisted public opinion and sent Japanese troops to Iraq, brought up the topic with Bush during the Group of Eight economic summit at Sea Island, Ga., early last month.

Japanese doctors who examined Jenkins in Jakarta, the Indonesian capital, have determined that he is suffering from a post-operative illness related to stomach surgery, as well as ailments related to internal organs. A Japanese official familiar with his condition said it was "more serious than we thought" but "not life-threatening."

On Thursday, Baker said in an interview with foreign correspondents that the United States was "sympathetic" to Jenkins's health condition. While the Bush administration maintains that Jenkins must eventually face charges, Baker appeared to leave open the possibility that the United States might not seek immediate custody of Jenkins if he came to Japan for medical treatment.

"It's certainly possible he could come to Japan, that the U.S. would insist on its rights, but the actual custody would not be something sought or consummated under some circumstances," Baker said.

In Washington, the State Department spokesman, Richard Boucher, said the United States would pursue Jenkins as an Army deserter. "Once he is in Japan, he becomes subject to the terms of the U.S.-Japan Status of Forces Agreement and falls under the authority of the U.S. military," he said at a briefing. Boucher said Jenkins has been charged with "extremely serious offenses" and "we intend to request custody when we have the legal opportunity to do so."

Koizumi has sought to reunite Soga, Jenkins and their daughters. Jenkins remained in North Korea with the couple's children when Soga returned for a tearful reunion with her family, from whom she was separated when she was kidnapped as a teenager by North Korean agents in 1978 for use in spy training camps in North Korea. Jenkins reportedly declined to accompany her to Japan in 2002, fearing arrest and extradition to the United States. But Japanese officials said Thursday that Jenkins has now expressed a desire to join his wife in Japan with their children.

Japanese news media have provided near-constant coverage of the Jenkins family reunion in Jakarta. When he descended from a Japanese government-chartered flight from Pyongyang last Friday, he sported a North Korean lapel pin, which he shed Sunday, attracting public interest. The gesture was quickly interpreted by Japanese media as an indication that Jenkins had left his allegiance to North Korea behind.

Staff writer Glenn Kessler in Washington and special correspondent Akiko Yamamoto contributed to this report.

The family of alleged U.S. Army deserter Charles Robert Jenkins was reunited last week in Jakarta, Indonesia.