"They'll continue to see a steady drumbeat of that kind of support, going forward," U.S. Defense Secretary Lloyd Austin told reporters a few days later at the Pentagon.

In a matter of weeks, however, the Taliban had seized most of the country, as well as any weapons and equipment left behind by fleeing Afghan forces.

Video showed the advancing insurgents inspecting long lines of vehicles and opening crates of new firearms, communications gear and even military drones.

"Everything that hasn't been destroyed is the Taliban's now," one U.S. official, speaking on the condition of anonymity, told Reuters.

Current and former U.S. officials say there is concern those weapons could be used to kill civilians, be seized by other militant groups such as Islamic State to attack U.S.-interests in the region, or even potentially be handed over to adversaries including China and Russia.

President Joe Biden's administration is so concerned about the weapons that it is considering a number of options to pursue.

The officials said launching airstrikes against the larger equipment, such as helicopters, has not been ruled out, but there is concern that would antagonize the Taliban at a time the United States' main goal is evacuating people.