Pictures and videos have shown the Taliban with firearms and vehicles that Pentagon troops used or provided to the Afghan national security forces, as well as advanced UH-60 Black Hawk attack helicopters and other equipment at the Kandahar airport.

"We don't have a complete picture, obviously, of where every article of defense materials has gone. But certainly, a fair amount of it has fallen into the hands of the Taliban," said White House National Security Advisor Jake Sullivan.

"Obviously, we don't have a sense that they are going to readily hand it over to us," he said.

Sullivan said losing control of millions of dollars worth of military supplies to an enemy is an example of "the difficult choices a president faces ... in the context of the end of a 20-year war."

He noted that the Black Hawks had been supplied to Afghan government forces to help battle the Taliban insurgency.

But the government forces succumbed to the Islamist insurgents quickly, and gave up control of large stores of weaponry and their helicopters.