The US agency that oversees the country’s nuclear stockpile will temporarily lay off about 1,400 of its employees as the government shutdown enters its 20th day.

Fewer than 400 employees will remain after the furloughs at the National Nuclear Security Administration (NNSA), a semi-autonomous agency within the US Department of Energy, a spokesperson told the BBC.

The department is tasked with improving national security by safeguarding the US’ nuclear stockpile and preventing the proliferation of nuclear weapons across the globe.

The NNSA has never furloughed workers before since its establishment in 2000. “We are left with no choice this time,” spokesperson Ben Dietderich said.

“We’ve extended funding as long as we could,” he said.