University of Virginia student Otto Warmbier arrives at the People’s Cultural House in Pyongyang for a news conference Feb. 29. (Kim Kwang Hyon/AP)

— North Korea is holding two U.S. citizens as “prisoners of war,” regime officials have told Americans lobbying for their release, as the months drag on with no word about the pair.

As missile launches and another nuclear test escalate tensions between the United States and North Korea, officials and analysts are growing increasingly concerned that the men will be held until after a new American president is elected.

There has been no word on Otto Warmbier, a business student at the University of Virginia, and Kim Dong-chul, a South Korean-born naturalized American citizen, since they were separately sentenced to years of hard labor in North Korean prisons in March and April, respectively.

[What it’s like to be an American held in North Korea]

In the intervening months, Kim Jong Un’s military has launched a stream of increasingly longer-range and more reliable missiles and conducted its fifth nuclear test . All the while, North Korea has been warning the United States that it will “mercilessly strike and wipe out” its enemies.

A University of Virginia student confessed to a "severe crime" during an orchestrated news conference in North Korea on Feb. 29. Here's how other U.S. citizens detained in North Korea have apologized to the country in recent years. (Victoria Walker/The Washington Post)

“I am certain that North Koreans will keep Otto Warmbier and Kim Dong-chul until after the U.S. election,” said Sue Mi Terry, a former North Korea analyst for the CIA who is now at Bower Group Asia, a consultancy.

“American prisoners are one of the few bargaining chips North Koreans” have, she said, and there is “zero incentive” for the North Koreans to release these Americans at this point. “Why waste it now with the Obama administration when there appears to be little progress that can be made in terms of either returning to talks or easing of the sanctions in place?”

This would be a departure from North Korea’s usual practice.

In recent years, the regime has made a habit of detaining U.S. citizens and using them as bargaining chips. This has followed a familiar pattern: arrest and harsh sentence, then release after a high-profile American flies to Pyongyang — as former presidents Bill Clinton and Jimmy Carter have done — to get them out.

[North Korea sentences college student to 15 years of hard labor]

These visits are portrayed in North Korea’s media as signs of the isolated state’s strength — a weak Washington begging to Pyongyang.

But in the case of Warmbier and Kim, there has been no request for a high-prestige envoy even four or five months after their sentencing, according to officials and others with knowledge of the discussions.

Kim Dong Chul, center, a U.S. citizen detained in North Korea, is escorted to his trial Friday, April 29, 2016, in Pyongyang, North Korea. (Kim Kwang Hyon/AP)

Nor has either man been trotted out to appear in front of journalists since their trials, even though there have been several opportunities.

The lack of progress has analysts and officials alike predicting that North Korea will try to use the men as leverage with the next administration.

“In the North Korean context, until there is some recognition from very high up among the elite that pardoning this person has some definite benefits for the state, there is really no incentive for them to recommend that,” said Daniel Pinkston, a longtime Korea analyst who now teaches at Troy University’s campus in Seoul.

At the same time, officials and family members seem to be trying to keep the case off the radar screen.

A spokesman for U-Va. said the university remained in touch with Warmbier’s parents, who did not respond to requests for comment. Young Pioneer Tours, which took the student to North Korea, declined to comment further.

But people advocating behind the scenes for the pair’s release describe conversations in which North Korean officials have referred to the two men as “prisoners of war.”

“This is a deeply offensive, even outrageous, characterization, and I and others have said as much to the North Koreans,” said one person involved in the discussions who spoke on the condition of anonymity because of the sensitive nature of the talks.

“There appears to be little or no interest in Pyongyang in talking about the terms of a possible release,” the person said.

This interpretation was shared by a senior administration official, who said: “They don’t appear to be interested in using them as hostages.”

[North Korea sentences former Va. man to 10 years of hard labor]

After eight years of “strategic patience” under the Obama administration — waiting for North Korea to change its calculus — the next administration will certainly launch a review of U.S. policy toward North Korea.

“I think the next administration will conclude that the path to Pyongyang — assuming there can be one — still goes through Beijing,” said Jonathan Pollack, a China and Korea expert at the Brookings Institution. “Perhaps Pyongyang reads this differently and believes that it can open a negotiating window by signaling a willingness to release Warmbier and Kim, assuming the price is right.”

Warmbier, 21, was arrested at Pyongyang airport on Jan. 2, at the end of a five-day tour to North Korea. But he wasn’t seen until the end of February, when he admitted in a highly choreographed news conference to trying to steal a political sign.

North Korea later released grainy CCTV footage, time-stamped 1:57 a.m. on New Year’s Day, showing a tall man pulling a propaganda sign off a hotel wall. The words are only partially visible, but what can be seen read: “Arm ourselves with strong socialism.”

Stealing or damaging this sort of poster could be considered blasphemous in a country where the Kims are deified. “It’s like going to Saudi Arabia and ripping down something about Muhammad, or ripping down a scroll about Jesus from the Vatican,” Pinkston said.

Because the United States does not have diplomatic relations with North Korea, the Swedish embassy in Pyongyang represents American interests there.

“Even when requested by the Swedish Embassy, however, [North Korea] still routinely delays or denies consular access to U.S. citizens,” said John Kirby, spokesman for the State Department.

[North Korea claims video shows student caught in act]

Swedish diplomats have not been granted access to Warmbier since March 2, Kirby said.

They were, however, present later that month when Warmbier was convicted of subversion and sentenced to 15 years in prison with hard labor.

A Washington Post journalist who visited Pyongyang in May repeatedly asked to see Warmbier, but the requests were denied.

In April, in a separate case, North Korea sentenced 62-year-old Kim Dong-chul to 10 years in prison with hard labor for “perpetrating . . . subversive plots and espionage” against the state.

In 2001, Kim, who became an American citizen in 1987 and lived in Fairfax County, Va., moved to the Chinese city of Yanji, on the border with North Korea.

Most recently, he had been working in the Rason Special Economic Zone, just over the border in North Korea, as head of a trade and hotel services company. He was arrested there, accused of trying to spread “religious” ideas in the North.

But Kirby declined to comment on whether the Swedish diplomats had seen him since his arrest and conviction. “We are aware of televised reports of another detainee in North Korea. Due to privacy considerations, I am unable to provide additional information,” he said.

The State Department strongly advises Americans against traveling to North Korea, warning of “the serious risk of arrest and long-term detention” for behavior that would not be considered criminal at home. Americans detained in North Korea could be “treated in accordance with ‘wartime law,’ ” says the latest advisory, updated last month.

Read more:

Did North Korea abduct an American in 2004 — to teach English to Kim?

North Korea defied world with nuclear test. Now it seeks aid for flood disaster.

After nuclear test, a new push to stop North Korea from sending workers abroad

Today’s coverage from Post correspondents around the world