WASHINGTON, Aug 23 (Reuters) - The United States" commitment to at-risk Afghans extends beyond President Joe Biden"s Aug. 31 deadline to withdraw from the country, a senior State Department official said, adding that the promise of safe passage did not have "an expiration date." "Our commitment to at-risk Afghans doesn"t end on August 31," the official told reporters in a briefing, without elaborating how Washington could continue its efforts to help people leave the country if it withdraws completely from the country by the end of the month. The Taliban seized power just over a week ago as the United States and its allies were withdrawing troops after a 20-year war launched in the weeks after the Sept. 11 attacks on the United States by al Qaeda militants in 2001. Panicked Afghans and foreigners have thronged the airport for days, clamoring to catch a flight out before the U.S.-led forces complete their pullout by the end of the month. "We"ve heard from the Taliban ... that they want a functioning airport well after the U.S. military has left ... The Taliban has also agreed to permit safe passage to the airport and this commitment doesn"t have an expiration date on it," said the official, speaking on the condition of anonymity. She added that even when U.S. military"s presence is gone the United States had every expectation that at-risk Afghans would have an opportunity to leave the country. But the reports from the ground already show potential evacuees face a perilous journey to the Kabul airport and chaos at the airport gates before they can soldier on through the crowds onto an aircraft. On Monday, one member of the Afghan forces was killed and several were wounded in an exchange of gunfire outside Kabul airport, while no U.S. personnel were hurt, the U.S. military said. NEW FLIGHT EN ROUTE TO U.S. A new flight carrying evacuated at-risk Afghans will arrive in the United States later on Monday from Ramstein air base in Germany, the official said in the same briefing, adding that the pace of flights will ramp up from transit hubs temporarily housing those evacuated from Kabul. There were currently eight transit hubs across six countries that were hosting more than 17,000 people. "The transit hubs that we have arranged in Germany, Italy and Spain will have the combined capacity to process approximately 15,000 people on a rolling basis, which in turn will enable us to keep evacuating people continuously from Kabul," the official said. Biden has said that the United States expects to evacuate between 50,000 and 65,000 people from Afghanistan. That is fewer than the number eligible for safe harbor, according to estimates by advocates. "Today the first onward flight of SIV applicants took off from Germany to the United States and we expect those to continue to ramp up," the official added, in reference to the Special Immigrant Visa, designed for people who worked with the U.S. military. The official also dismissed reports that only Americans were able to get through to Kabul airport and that others had been blocked.