WASHINGTON (AFP) - A US official working on closing the Guantanamo Bay prison has resigned, a Pentagon spokesman said Wednesday, the second senior US official tasked with closing the site who has resigned in weeks. Phillip Carter was appointed deputy assistant secretary of defense for detainee policy in April, but resigned last week due to personal and family reasons, said Pentagon spokesman Bryan Whitman. Carters departure comes days after President Barack Obama acknowledged that his administration would not be able to close the war on terror camp at the US naval base in Cuba by the January 22, 2010 deadline that he set. Obama had vowed during his first week in office in January that he would close Guantanamo within a year of taking office, saying that the prison camp does not adhere to US standards on human and civil rights and underlining his desire to break with the policies of his predecessor, George W. Bush. Some 215 suspects remain detained in Guantanamo. The White House announced on November 13 that Obamas top lawyer Greg Craig-a veteran Washington hand who led the effort to close Guantanamo-would resign effective January 3. Craig was an early supporter of Obama as he fought former first lady Hillary Clinton in the 2008 Democratic primary race. His resignation came just ahead of US Attorney General Eric Holders announcement that the self-proclaimed mastermind of the September 11, 2001 attacks, Khalid Sheikh Mohammed, and four other suspected terrorists held at Guantanamo Bay, will be tried in a civilian court in New York. The White House has said that it will continue to push for closing Guantanamo, and is moving to repatriate some detainees who have been cleared for release while seeking countries willing to provide asylum to others. Obama admitted in a November 18 television interview that his administration would miss the January 2010 deadline he set for closing the prison.