President Joe Biden on Friday said there is no plan for an imminent withdrawal of the final US troops in Afghanistan.

"No. We're on, we're on track exactly as to where we expect to be," he told reporters at the White House, following growing speculation the final contingents were due to leave within the next few days.

Biden has set a deadline of September 11 for the final pullout of the few remaining troops, following 20 years of war.

Biden responded to concerns that the internationally backed Afghan government might quickly crumble to Taliban insurgents once its foreign backers have fully left, saying they "have the capacity to be able to sustain government down the road."

The US military is keeping an "over the horizon capacity" which could bring firepower to help the government, but the "Afghans are going to have to be able to do it themselves."