John Bacon, and Jane Onyanga-Omara

USA TODAY

The Obama administration demanded North Korea release an American college student sentenced Wednesday to 15 years of hard labor for allegedly pilfering a propaganda banner as a souvenir.

Officials arrested University of Virginia student Otto Warmbier, from Wyoming, Ohio, for allegedly "perpetrating a hostile act" in Pyongyang while traveling with a tour group in January. The nation's supreme court in a one-hour trial convicted Warmbier of subversion and meted out the punishment.

White House Press Secretary Josh Earnest accused North Korea of using “U.S. citizens as pawns to pursue a political agenda.”

Tensions between the U.S. and North Korea have reached a fever pitch after the communist nation tested international patience by launching missiles. The U.S. has sought tougher sanctions against the country.

The allegations against Warmbier "would not give rise to arrest or imprisonment in the United States or in just about any other country in the world," Earnest said.

State Department spokesman Mark Toner urged North Korea to grant Warmbier a special pardon and release him.

Bill Richardson, a former U.S. ambassador to the United Nations, told the Associated Press he met with North Korean diplomats in New York on Tuesday to request Warmbier’s release. Richardson said based on past experience, North Korea could release Warmbier after sentencing.

“My concern now is that the U.S.-North Korean relationship is in very low, negative ebb, and I hope that does not affect a humanitarian negotiation for the release of Otto,” Richardson told AP.

The tour company, Young Pioneer Tours, which specializes in tours to North Korea, said it was working with "relevant authorities" to obtain Wambier's freedom, but North Korea said Warmbier's traveled as a tourist to disguise his real aim of destroying the unity of the nation with "the tacit connivance of the U.S. government."

At the University of Virginia, classmates reacted with disbelief to his sentencing.

“It doesn’t feel real, this just doesn’t happen to people. I can’t comprehend it," said student Alaina Patrick, who lived in the same dorm as Warmbier, and recalled that some hallmates had “crushes” on him.

Teachers and coaches at Wyoming High School where Warmbier, 21, graduated as salutatorian in 2013, describe him as a "great kid," a "leader" and an outstanding student. He studies economics and global sustainability at the University of Virginia, which said it was in touch with his family.

Two weeks ago, North Korean officials presented Warmbier to the media in Pyongyang, where he apologized for trying to steal the banner from a staff-only area of the hotel where he was staying. He said he wanted it as a trophy for a church member in Wyoming. He called it the worst mistake of his life.

"On the early morning of Jan. 1, 2016, I committed my crime, of taking out the important political slogan from the staff-only area of the Yanggakdo International Hotel, which aimed at harming the work ethic and the motivation of the Korean people,” a weeping, trembling Warmbier told reporters. "I beg you, the people and government of the DPRK, for your forgiveness," he said, referring to the Democratic People's Republic of Korea, the North's official name.

Contributing: Gregory Korte, Hannah Hall

U.S. student detained in North Korea apologizes