WASHINGTON, Aug 24 (Reuters) - President Joe Biden has agreed with a Pentagon recommendation to stick with the Aug. 31 Afghanistan withdrawal deadline, an administration official told Reuters on Tuesday. U.S. President Joe Biden delivers remarks on the coronavirus disease (COVID-19) response and vaccinations during a speech in the Eisenhower Executive Office Bulding"s South Court Auditorium at the White House in Washington, U.S., August 23, 2021. REUTERS/Leah Millis The Pentagon recommendation was made on Monday based on concerns about security risks to American forces, the official said. Biden has asked the Pentagon for contingency plans to stay longer should it be necessary, the official said, speaking on condition of anonymity. The United States is telling the Taliban that the U.S. withdrawal by Biden"s Aug. 31 deadline is contingent on the group"s cooperation in facilitating evacuations, the official said.