SEOUL (Reuters) – The only western-funded university in North Korea is scrambling to recruit teachers not from the United States after a U.S. travel ban to the isolated country forced the school to start the September semester with only half of its faculty.

According to a recruitment notice from a faculty member of Pyongyang University of Science and Technology (PUST) reviewed by Reuters, the school is on a “vigorous lecturer recruitment campaign” for the spring semester slated to start next year.

The notice, which said the recruitment focus is “non-U.S. professors” mainly from Asia and Europe, suggests that discussions with the U.S. State Department about receiving special exemptions for PUST’s volunteers have not gone well.

Of the roughly 130 foreigners at PUST including faculty members, staffers and family members, about 60 had been U.S. citizens, according to people familiar with PUST operations.

“Needless to say, our chronic faculty shortage and curriculum instability have been exacerbated even further, translating into the emergency situation of crippled school operation and curriculum running,” said the notice sent out by Paul Song, currently acting dean of the international finance and management department at PUST.

As of Sept. 1, the U.S. State Department has enforced a ban on Americans traveling to North Korea following the death earlier this year of an American student who had been detained by the state while on a tour. It also advised U.S. citizens living there to leave.

North Korea has criticized Washington’s decision to ban U.S. passport holders from visiting the North, with state media describing it as a “sordid” attempt to limit human exchanges. It has also said its doors are always open for all Americans who wish to visit.

Tensions on the Korean peninsula have escalated significantly in the wake of numerous missile tests and its sixth and most powerful nuclear test by Pyongyang last month.

Insults and threats exchanged between the North’s leader Kim Jong Un and U.S. President Donald Trump have also exacerbated global jitters over possible military conflict.

A month after the fall semester had started, a PUST official told Reuters high security concerns over North Korea has made it “difficult to find additional replacement staff”.

“A number of organizations are unwilling to approve staff to travel,” the official added.

The school was founded in 2010 by a Korean American evangelical Christian with the goal of helping North Korea’s future elite learn the skills to modernize the North and engage with the outside world.

Since its founding, the school has grown to about 500 undergraduate and 60 graduate students studying in mostly three departments – electronic and computer engineering, international finance and management and agriculture and life sciences.