This 2005 photo provided by the Palo Alto Weekly shows Merrill Newman, a retired finance executive and Red Cross volunteer, in Palo Alto, Calif. The 85-year-old American veteran of the Korean War has been detained in North Korea since last month. The son of Merrill Newman told the San Jose Mercury News on Wednesday his father was taken off a plane set to leave North Korea on Oct. 26. (Nicholas Wright/AP)

A blunt warning from the State Department this week, telling Americans not to travel to North Korea for any reason, was the first clue that something in the perpetually difficult U.S. relationship with North Korea had suddenly gotten worse.

The State Department warned of “arbitrary arrest and detention” but gave no details about the case that apparently prompted the advisory. An 85-year-old Korean War veteran from California has been in a North Korean jail for more than a month after being forcibly escorted off a plane during a visit.

Merrill Newman and a friend from his Palo Alto retirement complex had gone to the secretive communist country, sometimes called the “hermit kingdom,” to revisit some of their wartime experiences.

Newman’s imprisonment had been kept secret in hopes of quietly winning his release, but his family acknowledged it this week. The State Department still will not confirm the detention. Unless an individual waives rights under the Privacy Act, the government is barred from discussing details of his or her travel.

But people familiar with the case confirmed Newman’s captivity and the behind-the-scenes U.S. diplomatic efforts to free him. Newman has received no visits in detention from U.S. officials or, apparently, from Swedish diplomats, who act as intermediaries between the United States and North Korea because the two do not have regular diplomatic relations.

An 85-year-old Korean War veteran has been detained in North Korea. His California family is pleading for his release. (REUTERS)

A uniformed North Korean officer boarded the plane Oct. 26 and demanded Newman’s passport, Newman’s son Jeffrey Newman told the Associated Press.

“My dad got off, walked out with the stewardess, and that’s the last he was seen,” Jeffrey Newman told the news service at his home in Pasadena, Calif.

Jeffrey Newman did not return telephone and e-mail requests from The Washington Post for comment.

Jeffrey Newman has told interviewers that, during his father’s visit to North Korea, he had at least one discussion with North Korean officials about his wartime experiences. The elder Newman was an infantryman during the 1950-53 war.

The war ended in an armistice, not a peace treaty, leaving the Korean Peninsula technically at war 60 years later.

Asked about the Newman case during a visit to China, Glyn T. Davies, the top U.S. official in charge of North Korea policy, acknowledged the news reports but said he could not comment.

Davies has made little headway in efforts to restart stalled nuclear disarmament talks with North Korea and told reporters Thursday that he sees little sign that will change for now. Snatching visiting Americans doesn’t help, he allowed.

“It’s very important that, as a matter of principle, we always keep consular problems and issues set aside from political issues,” Davies said. “But it is true that North Korea could send a very different signal about its interest in having a different sort of relationship with the United States were it to take that step of releasing our citizens, and it’s a matter of some wonderment to me that they haven’t yet moved on that.”

Davies was referring directly to the case of another imprisoned American, Kenneth Bae, whose release the United States has sought for a year, and indirectly to Newman.

Jeffrey Newman told the AP that his father, who traveled widely after retiring as a finance executive, had long wanted to visit North Korea and had studied the language ahead of his scheduled nine-day trip.

Nothing is known publicly about the conditions of Newman’s imprisonment or his health behind bars.

North Korea’s official state-run media have not mentioned the detention, first reported by the San Jose Mercury News and Japan’s Kyodo News service.

The younger Newman said the Swedish ambassador had delivered his father’s heart medication to the North Korean Foreign Affairs Ministry, but it is not clear whether Newman received it.

The State Department has allowed U.S. tourism in North Korea since 1995 but has long cautioned Americans about the risks of visiting an unpredictable country that regularly accuses the United States and U.S. ally South Korea of plotting attacks.

A growing number of Americans visit North Korea every year on state-monitored tours. North Korea has encouraged the tourism, which is a source of badly needed hard currency for a government under heavy international sanctions.

Max Fisher contributed to this report.