The withdrawal of US forces from Afghanistan is more than 90 per cent completed, the Pentagon's Central Command announced on Tuesday.CentCom said it had officially handed over seven former US bases to the Afghan security forces and had evacuated the equivalent of nearly 1,000 C-17 air freighter loads of equipment from the country, ahead of the September deadline to complete the pullout.

On Friday US forces handed over the sprawling Bagram air base north of Kabul, the main centre of US military operations in the country for most of the past two decades of conflict.

Tuesday's announcement underscored that most of the process of withdrawing US military and civilian personnel ordered by President Joe Biden in April had been completed.

At the time of Biden's order, there were officially 2,500 US troops and 16,000 private contractors.

According to reports, there were also some 1,000 US special forces operating in Afghanistan at the time as well not included in the official tally.

While Biden had set a deadline of September -- the 20th anniversary of the Afghan-based Al-Qaeda attack on the United States that sparked the American invasion of the country -- the Pentagon has moved quickly to reduce its presence to a minimum this month.

"We expect it to be completed by the end of August," White House press secretary Jen Psaki said on Friday after the Bagram handover.

The United States is expected to keep a reported 650 or more military personnel in the country to protect the US embassy and diplomats.