Washington, D.C. ? The United States said Wednesday that American experts working at North Korea’s main nuclear plant have been asked to leave the country, further heightening tension following the North’s firing of a rocket earlier this month over U.S. ally Japan.

State Department spokesman Robert Wood told reporters that the four U.S. officials monitoring the North’s disablement of its Yongbyon nuclear plant are now making preparations to leave.

“It’s a step backward,” Wood said. “The North is going to have to deal with the consequences of such decisions. And they just bring upon themselves further isolation from the international community.”

The expulsions come amid North Korean fury at international condemnation of its rocket launch.