LONDON, Aug 23 (Reuters) - Britain still wants to fly out thousands of people out from Afghanistan and has not set a hard deadline for when evacuations will end, Prime Minister Boris Johnson"s spokesperson said on Monday. Johnson will ask U.S. President Joe Biden to extend the evacuation deadline from Afghanistan when the Group of Seven leaders discuss the crisis on Tuesday. "We have not set a hard deadline for when the evacuation procedure will end," the spokesperson said. "We will continue to run our evacuation process as long as the security situation allows, like I said this will be a topic of discussion tomorrow, and we need to flexible in our approach."