U.S. officials say the Trump administration will ban American citizens from travelling to North Korea following the death of university student Otto Warmbier, who was returned to the U.S. in a coma after spending time in a North Korean prison.

The officials said Friday that Secretary of State Rex Tillerson had determined to implement a "geographical travel restriction" for North Korea, which would make the use of U.S. passports to enter the country illegal.

They said the restriction would go into effect 30 days after a notice is published in the Federal Register, but it was not immediately clear when that would be. There was no announcement in Friday's editions of the government publication.

The officials were not authorized to publicly discuss the decision before it is announced, and spoke on condition of anonymity.

Warmbier, a 22-year-old University of Virginia student who spent more than a year in captivity, died in the U.S. last month after he was released by North Korea and returned home to Ohio.

Warmbier had confessed he tried to steal a propaganda banner while visiting with a tour group. He had been sentenced to 15 years with hard labour for subversion.

U.S. tourist Otto Warmbier, centre, died last month shortly after he was released from a North Korean prison. (Kyodo/Reuters)

The U.S., South Korea and others often accuse the North of using foreign detainees to wrest diplomatic concessions. At least three other Americans remain in custody in North Korea.

Simon Cockerell, Beijing-based general manager of the Koryo Group, one of the leading organizers of guided tours to North Korea, said the ban would affect 800 to 1,000 Americans who visit North Korea annually. Although Pyongyang does not publish exact figures, Americans are thought to account for a mere one per cent of all foreign visitors.

Westerners make up five per cent of total visitors, Americans about 20 per cent of the Western contingent, according to statistics.

Cockerell said the ban would likely have a tangible impact on business for his and similar outfits, and said that would turn back the clock on engagement with the North.

"It's unfortunate because we criticize North Korea for being isolationist and now we're helping isolate them," Cockerell said. "That's not what soft power is about."