"We are working very hard (and) we remain hopeful that we will be able to operate it as soon as possible... hopefully in the next few days we will hear some good news," he said.

For America, Biden argued, the only choice in Afghanistan was "leaving or escalating."

Taken with a night vision device from a side window of the C-17 transport plane, the ghostly green and black image of the general striding toward the aircraft waiting on the tarmac at Kabul's Hamid Karzai Airport was released by the Pentagon hours after the United States ended its 20-year military presence in Afghanistan.

The last of the American troops overseeing a desperate evacuation effort flew out of Kabul airport on Monday night, completing a withdrawal that has raised deep questions about the United States' status as a superpower.