The United States confirmed Thursday it will ask Japan for custody of a former U.S. soldier accused of deserting to North Korea in 1965. The unusual case of Sergeant Robert Jenkins could strain U.S.-Japanese relations.

Officials here say that while Sergeant Jenkins disappeared from his post in South Korea nearly 40 years ago, he is still technically considered an active member of the U.S. military, and as such the United States will request his return from Japan.

Now 64 years old, Sergeant Jenkins was posted near the Demilitarized Zone in 1965 when, officials say, he crossed into North Korea and later took part in anti-U.S. propaganda activities.

While living in North Korea, he married a Japanese woman who had been abducted to the communist state by North Korean agents.

She was returned to Japan three years ago along with other abductees, while Sergeant Jenkins, wary of prosecution by the United States, stayed behind in Pyongyang.

The case took a new turn this month when Sergeant Jenkins was reunited with his wife and two daughters in Jakarta. Japanese officials announced he will fly to Japan as soon as Sunday for medical treatment, triggering a round of U.S.-Japanese consultations on his custody.

At a news briefing, State Department spokesman Richard Boucher said the U.S. view is that Sergeant Jenkins is a deserter from the Army, charged with extremely serious offenses, and that United States will request his hand-over under the bilateral agreement governing the presence of U.S. troops in Japan.

"We do understand that the Japanese government plans to bring Sergeant Jenkins to Japan later this week to undergo emergency medical treatment, and once he's 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. The Status-of-Forces agreement gives us the right to request custody of Sergeant Jenkins, and we intend to request custody when we have the legal opportunity to do so," Mr. Boucher said.

A senior diplomat who spoke to reporters here said the United States has been actively discussing the issue with Japan, but that to this point there has been no deal or arrangement made under which Sergeant Jenkins would be handed over to U.S. custody.

The diplomat said the United States believes Japan is obligated to turn him over, and he declined to speculate what the ramifications might be if Tokyo refused, saying, "I don't want to start making an issue of it, unless I know it's going to become an issue."

Japanese officials have said Sergeant Jenkins suffers from an abdominal inflammation and other medical conditions and will be hospitalized immediately on his arrival in Japan.

Spokesman Boucher said the United States will take Sergeant Jenkins' medical condition into account, and left open the prospect that he might not be handed over to American custody until after he receives treatment.

Sergeant Jenkins faces prosecution on a number of charges including desertion, aiding the enemy, and soliciting other soldiers to desert, offenses that could bring punishments of up to life in prison.

The Jenkins case has become a national issue in Japan, largely because of his marriage to the Japanese woman, whose return home was arranged by Prime Minister Junichiro Koizumi at a 2002 meeting with North Korean leader Kim Jong-Il.