The U.S. government expressed regret Monday over North Korea’s threat to shut down an inter-Korean industrial complex in Gaeseong.

“Closing it would be regrettable, given that more than 50,000 North Korean people are employed there, and it would not help them achieve their stated desire to improve their economy and better the lives of their people,” Patrick Ventrell, a spokesman for the State Department, said at a press briefing. “So that would be a regrettable action, if they continue in that direction.”

He said the U.S. remains in close consultation with South Korea on the issue.

In a step to highlight soaring military tensions on the peninsula, the North has pulled all of its workers from the Gaeseong industrial park, putting it into the biggest crisis since it was created nine years ago as a symbol of nascent inter-Korean reconciliation.

Pyongyang will temporarily halt the operation and review whether to keep it alive, Kim Yang-Gon, a senior ruling party official, said in a statement Monday carried by the North‘s official news agency, KCNA.

The announcement came as the U.S. and its regional allies are closely monitoring the reclusive communist nation for possible missile and nuclear tests or direct attacks.

Ventrell would not be drawn into questions on that possibility, saying it’s a matter of intelligence.

He said the U.S. is continuing to urge China and Russia to dissuade North Korea from taking additional provocations.

“This is true for both Beijing as well as our counterparts in Moscow, the Russians. We encourage the Chinese to make their case to Pyongyang that they have to refrain from provocative rhetoric and threats,” he said. “So we‘ll continue to work with the Chinese. We’ll continue with the Russians and other partners to get North Korea to abide by its obligations.”

Ventrell said his department has no exact tally on American citizens staying in North Korea.

“We don‘t require U.S. citizens to register or come to us when they travel abroad, so it’s not possible for us to have exact numbers,” he said. But he estimated that hundreds of U.S. citizens are there, mostly engaged in humanitarian work.

The U.S. has no embassy or consular office in the North as they have no formal diplomatic ties. (Yonhap News)