LONDON (Reuters) -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 defence minister Ben Wallace said.

       U.S. President Joe Biden will face pressure to extend an Aug. 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 they will reject any demands by Western forces to extend the deadline to allow more time to complete the evacuation operation.

       Biden said on Sunday that he would not like to extend the deadline for evacuations, but that talks were ongoing.

       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."

       Wallace said if Western forces do not leave by the deadline the Taliban could attack the airport or prevent people arriving.

       "If that airport gets attacked then effectively it closes down, mortar fire onto the runway etc, and then you are left with a very big humanitarian problem," he said.

       Britain has evacuated around 8,600 people from Afghanistan in last two weeks, including 2,000 people in the last 24 hours, Wallace said. But Wallace said given the limited time before the evacuation window closes, "we're not going to get everybody out".

       (Reporting by Andrew MacAskill; editing by Costas Pitas)