LONDON, Aug 24 (Reuters) - The U.S. government is unlikely to extend the evacuation window to allow its citizens and Afghans more time to fly out of Kabul, British defence minister Ben Wallace said ahead of emergency talks by G7 leaders. U.S. President Joe Biden will face pressure to extend an Aug. 31 deadline to evacuate thousands seeking to flee the Taliban in Afghanistan at a virtual meeting of the leaders of the Group of Seven wealthy nations on Tuesday. read more 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, but that talks were ongoing. "I think it is unlikely," Wallace told Sky News. "Not only because of what the Taliban has said but also if you look at the public statements of President Biden." He added: "It is definitely worth us all trying, and we will." Members of the UK Armed Forces continue to take part in the evacuation of entitled personnel from Kabul airport, in Kabul, Afghanistan August 19-22, 2021, in this handout picture obtained by Reuters on August 23, 2021. LPhot Ben Shread/UK MOD Crown copyright 2021/Handout via REUTERS 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. Wallace has said that there is no prospect of British troops continuing the evacuation effort in Kabul without the presence of the U.S. military. In the future, Wallace said that while Britain prefers the United States as a military ally, it may look to form alliances with other countries for specific operations. "It may actually be more in our interest to join with other partners and we must have a force that is much more able to be interoperable as opposed to dependent," he said. Britain has evacuated around 8,600 people from Afghanistan in last two weeks, including 2,000 in the last 24 hours, Wallace said. But given the limited time before the evacuation window closes, "We"re not going to get everybody out," he added.