US House Intelligence Committee Chairman Adam Schiff, speaking to reporters on Monday after a briefing by intelligence officials, said he thinks it is very unlikely the evacuation of Afghanistan will be completed by an August 31 deadline.
"I think it's possible but I think it's very unlikely given the number of Americans who still need to be evacuated," Schiff said.
Western governments are unlikely to extend the evacuation window to allow their citizens and Afghans more time to fly out of Kabul airport, Britain's defense minister Ben Wallace said.
US President Joe Biden will face pressure to extend an August 31 deadline to evacuate thousands seeking to flee the Taliban in Afghanistan when he meets Group of Seven leaders at a virtual meeting on Tuesday.
The Taliban have said the August 31 deadline is a red line.
Wallace told Sky News he was doubtful there would be an extension "not only because of what the Taliban has said but also if you look at the public statements of President Biden, I think it is unlikely."
He added: "It is definitely worth us all trying and we will."