As of Monday, the United States had "retrograded" the equivalent of enough gear to fill 104 C-17 Globemasters, the military's massive transport, Centcom said in a statement using the Pentagon's term for the pullout.

They had also turned over more than 1,800 pieces of equipment to a separate logistics agency from destruction.

US forces have also turned over one of the bases, Camp Antonik in Helmand Province, to Afghan forces.

Centcom estimated that it had completed between six and 12 percent of the retrograde process.

The US military is declining to be precise about the speed of the withdrawal and likely final date in order to "preserve operational security."

In April President Joe Biden ordered the military to withdraw its last 2,500 troops and some 16,000 civilian contractors who support coalition operations from the country by September 11, 2021, the 20th anniversary of the Al-Qaeda attacks on the United States which led to the US invasion of Afghanistan, where the extremist group was based.