Aug 19 (Reuters) - Britain"s last evacuation flight could leave Kabul in five days under an accelerated timetable for withdrawal from Afghanistan, The Times newspaper reported. Ministers were told earlier this week that the last evacuation flight might have to leave next Tuesday before the planned departure of American forces on Aug. 31, the newspaper reported, citing sources. Another government source was quoted as saying the Tuesday evacuation date had not yet been formally agreed. Britain is unable to evacuate unaccompanied children from Afghanistan, Defence Secretary Ben Wallace said on Thursday when asked about footage of a young child being handed over a wall to Western soldiers at Kabul airport. A spokeswoman for Britain"s foreign ministry said about 1,200 people had left Kabul on flights for the UK since Sunday. read more Britain is working with the Taliban in Kabul on a "tactical, practical level" to evacuate citizens and eligible Afghans, Britain"s ambassador to Afghanistan said on Wednesday. read more The Taliban seized power last weekend in an upheaval that sent thousands of civilians and Afghan military allies fleeing for their safety. Reporting by Kanishka Singh in Bengaluru; Editing by Peter Cooney Our Standards: The Thomson Reuters Trust Principles.