SEOUL, South Korea — The only foreign-funded private university in North Korea started a new semester on Monday, but without its usual American professors because of Washington’s ban on travel to the country, university officials said.

The travel ban, which took effect Friday, has threatened the operation of Pyongyang University of Science and Technology, a school in the North Korean capital that was financed by evangelical Christians abroad.

The university has been relying on 60 to 80 volunteer professors from the outside, about half of them Americans. It can no longer accept American volunteers unless it wins exemptions from the travel ban.

For now, the fall semester started with 20 to 25 non-American foreign volunteers, according to Colin McCulloch, the university’s director of external relations.