The U.S. is evacuating a "significant" number of employees from its embassy in Kabul, Afghanistan, as Taliban forces gain ground across the country.

The State Department announced on Thursday it is reducing its civilian footprint of roughly 4,000 personnel to a "core diplomatic presence" given the rapidly deteriorating security situation in Afghanistan.

"Our embassy remains open and our diplomatic mission will endure," State Department spokesperson Ned Price said at a news briefing.

Meanwhile, embassy officials have been urging Americans to leave Afghanistan immediately over the last few days.

An additional 3,000 U.S. troops are heading to Afghanistan to assist with the evacuation efforts, according to the Pentagon. Three infantry battalions are expected to arrive at Kabul's international airport in the next 24-48 hours.