Planning to be out of the country by 11 September, the command believes the withdrawal is somewhere between 16% and 25% finished.
US forces have already returned five installations that they control to the Afghan Defence Ministry.
Approximately 160 C-17 transport aircraft loads of material and equipment have left Afghanistan, with 10,000 pieces of military equipment additionally turned over to the Defense Logistics Agency.
After 20 years, the US is leaving Afghanistan because the mission there is complete, said Pentagon Press Secretary John F Kirby during a press briefing on Tuesday.
"The president has been very clear that our troops accomplished the mission for which they were sent to Afghanistan," he said.
"That was to prevent the country from being used as a safe haven for terrorist attacks on our homeland, and there hasn't been another attack on the homeland emanating from Afghanistan since 9/11.
"So the president believes the mission has been completed."
Mr Kirby said the new mission for the US was the withdrawal of their forces and the development of a new relationship with the government of Afghanistan and the Afghan National Defence and Security Forces.
The United States will create a "new bilateral relationship with Afghanistan across the government: diplomatically, economically, politically and certainly from a security perspective," Mr Kirby said.
"Our relationship with Afghan National Defense and Security Forces will continue, but it will continue in a different way."
Mr Kirby did stress, however, that the planned withdrawal did not mean leaving the region outright, citing further potential threats, which the US would meet by strengthening their existing "over-the-horizon" capabilities and growing new ones.
He said the US already has some over-the-horizon capacity in the region, by virtue of forces already stationed there and long-range capabilities that are outside the region.
"We know we need to think through this more deliberately and more thoughtfully going forward as we get closer to completing the withdrawal, and we're working on that," he said.
The withdrawal update comes as NATO announced it will continue training Afghan special forces outside the country after completing its troop withdrawal.
Jens Stoltenberg said NATO plans to provide training "outside Afghanistan, focusing on Special Operations Forces", but it is not clear where the training will take place.
America's longest-serving commander in Afghanistan told the BBC last week that "history will judge" the success of coalition forces' presence in the country.
British troops are among the coalition forces leaving Afghanistan as part of the withdrawal.
Cover image: US trucks carrying munitions from Afghanistan arrive at a base in Kuwait (Picture: US Department of Defense).