US defense officials in charge of evacuating Americans from Kabul claimed on Tuesday morning they would fly 5,000 a day out despite only managing to rescue 1,400 in the three days since the city fell, while as many as 40,000 may remain stranded - some in remote parts of the country.

The Taliban is fast encroaching on the airport in Kabul and its fighters are now in charge of every access point on the way from the city. They have set up guard at the airport's entrance which means NATO troops are relying on their cooperation to safely get foreign nationals and Afghan refugees through the gates and onto planes. 

At a White House briefing on Tuesday afternoon, Biden's National Security Advisor Jake Sullivan confirmed US forces were 'in contact' with the Taliban negotiating how to get Americans, Afghan refugees and other foreign nationals in safely and onto planes. 

'We are in contact with the Taliban to ensure the safe passage of people to the airport,' he said. 

It puts the lives of Afghan nationals who helped the US and are now desperate to flee in an impossible situation of being unable to stay and live under them, but also too terrified to present themselves at the airport to the terrorist soldiers who they fear will slaughter them for working against them for 20 years. 

The State Department has been deliberately vague on the number of Americans who remain in Afghanistan and who they are.

Pentagon spokesman John Kirby said on Tuesday morning that between 5,000 and 10,000 are in Kabul, but earlier admitted he had no idea how many there were or where they were. George W. Bush's former Assistant Secretary of State, Robert Charles, says there are between 15,000 and 40,000 'scattered' across all of Afghanistan.