The United States will prohibit its citizens from traveling to North Korea as tourists starting from late next month, tour operators said Friday, amid high tensions between the two countries.

The decision is expected to be announced by the U.S. government next Thursday and the ban is likely to become formally effective 30 days later, Simon Cockrell, general manager of Koryo Tours, a Beijing-based travel agency that organizes North Korea tours, told Kyodo News.

He said the company was informed in the afternoon of the new policy by the Swedish Embassy in Pyongyang, which represents U.S. interests in North Korea as the two countries have no diplomatic ties.

The travel ban will be introduced following the death about a month ago of American university student Otto Warmbier, who was released by North Korea in a coma after he was detained in January 2016 while on a tour.

"We have been informed that the U.S. government will no longer be allowing U.S. citizens to travel to (North Korea)," Young Pioneer Tours, which took the 22-year-old student to the country, also said on its website. "After the 30-day grace period any U.S. national that travels to North Korea will have their passport invalidated by their government."

Warmbier was convicted for what North Korea said was a hostile act against Pyongyang in his attempt to steal an item with a propaganda slogan in a staff-only area of his hotel.

Before he was medically evacuated from North Korea, he was serving a 15-year prison term with hard labor.

Following his death, U.S. President Donald Trump said that Washington "once again condemns the brutality of the North Korean regime as we mourn its latest victim."

"Otto's fate deepens my administration's determination to prevent such tragedies from befalling innocent people at the hands of regimes that do not respect the rule of law or basic human decency," Trump said in a statement.

The release of Warmbier on June 13 came while North Korea is being increasingly isolated from the international community over its defiant pursuit of nuclear arms and missile technology.

After a series of weapons tests in recent years, North Korea this month conducted its first test-firing of an intercontinental ballistic missile. If launched at a normal trajectory, the missile could have flown about 8,000 kilometers, a distance easily capable of covering the U.S. states of Alaska and Hawaii.

While three more U.S. citizens are still being held in North Korea, U.S. officials are concerned over the country's track record of detaining foreigners to use them as diplomatic pawns.

Tomas Ojea Quintana, the U.N. special rapporteur on North Korea's human rights situation, told a press conference in Seoul on Friday that the Warmbier case was "a reminder to all of us of the dire consequences of the lack of access to consular and legal counsel for those in detention in North Korea."

The general manager of Koryo Tours said that while specifics of the travel ban remain unclear, what is certain is that no U.S. citizens will be allowed to visit North Korea for tourism purposes.

Some 4,000-4,500 Western tourists have visited North Korea each year and those from the United States have accounted for about 20 percent, according to Cockrell.

"It's not great," Cockrell said of the ban.

He believes tourism has an important role in offering a glimpse into the lives of ordinary North Koreans and giving them rare opportunities at the same time to contact with people from the rest of the world.

(Young Pioneer Tours)