WASHINGTON (AP) — Kansas Republican Sen. Pat Roberts is blocking a vote on the nomination of Eric Fanning to be the next Army secretary. At issue are efforts by the president to close the prison at Guantanamo Bay, Cuba, and transfer detainees to the United States.

Republican Sen. John McCain tried to secure a vote on Fanning, who if confirmed would be the first openly gay leader of a U.S. military service.

But Roberts objected on Thursday, saying he won’t relent until the White House promises no detainees will be moved to Fort Leavenworth in Kansas.

McCain says it’s unfair to block Fanning’s nomination over an unrelated issue. McCain calls it a distortion of the Senate’s advise and consent role.

Fanning has served in several roles at the Pentagon.