US to bar Americans from traveling to North Korea

— -- Americans will soon be barred from traveling to North Korea, the U.S. State Department has announced.

The U.S. government will invalidate the passport of any American citizen traveling to, through, or in North Korea, beginning sometime in August.

The ban will apply to all U.S. citizens, but dual citizens may be able to travel on their other passport, with the State Department specifying in its statement, "U.S. passports will be invalid for travel."

There will also be waivers available, but only for "certain limited humanitarian or other purposes."

The State Department will file a notice in the Federal Registrar sometime next week, and 30 days after that, the ban will begin.

Two of the biggest tour companies that bring American tourists to the reclusive country were the first to announce the news. Koryo Tours and Young Pioneers Tours - the group that organized Otto Warmbier’s trip – both said that they were contacted and told the news. Koryo Tours general manager Simon Cockerell told ABC News that the Swedish embassy in the Democratic People's Republic of Korea, the U.S.’s diplomatic liaison in the country, informed his company of the decision.

Warmbier was a 21-year-old University of Virginia student who was arrested in North Korea in January 2016 while visiting the country as part of a tour group, held captive by the regime for a year and a half and at some point fell into a coma. He was evacuated and died June 19 of this year, days after returning home. The circumstances of how he fell into a coma are shrouded in darkness, but his case has provoked outrage and concern about other Americans’ safety.

There are dozens of U.S. citizens living in North Korea, including as many as 50 Americans teaching at North Korea’s only private university, Pyongyang University of Science and Technology, according to the school's spokesman Colin McCulloch. Two of the three Americans still held by North Korea were teaching there.

"Clearly, we have to ask some sort of exemption or else it's a show-stopper for us," McCulloch, who is also a business professor at PUST, told ABC News. "If we didn't get an exception, we would basically have to stop our work ... because we would not be able to provide enough personnel."

In past years, somewhere between 800 and 1,250 Americans visit North Korea each year, although that number has declined sharply this year following the recent death of Warmbier.

The travel ban is officially known as a geographic travel restriction, which gives the secretary of state the ability to bar travel to country if it is "at war with the United States; armed hostilities are in progress in the country; or there is imminent danger to the public health or physical safety of U.S. travelers in the country," according to the State Department.

Violators could be prosecuted, although such prosecutions are rare. Most recently, geographic travel restrictions were implemented for Lebanon from 1987 to 1997, Iraq from 1991 to 2003, and Libya from 1981 to 2004.

ABC News's Ben Gittleson contribtued to this report.