KABUL, Afghanistan (AP) — The NATO Resolute Support mission in Afghanistan says two U.S. service members have been killed.

A brief statement says the two were killed Wednesday and their names are being withheld until 24 hours after their next of kin are notified, in accordance with Pentagon policy.

The statement doesn't say how they were killed.

More than 2,400 U.S. service personnel have died in Afghanistan since the U.S.-led invasion in 2001 to topple the Taliban, whose government had harbored al-Qaida leader Osama bin Laden.

Now, the U.S. and Taliban are in negotiations on an end to nearly 18 years of fighting — America's longest war.

The U.S. formally ended its Afghan combat mission in 2014 but still provides extensive air and other support to local forces battling both the Taliban and an affiliate of the Islamic State group.