By ELLEN KNICKMEYER, Associated Press WASHINGTON (AP) — Khalid Sheikh Mohammed, accused as the main plotter in al-Qaeda’s Sept. 11, 2001, attacks on the United States, has agreed to plead guilty, the Defense Department said Wednesday, pointing to a long-delayed resolution in an attack that altered the course of the United States and much of the Middle East. He and two accomplices, Walid Bin Attash and Mustafa al-Hawsawi, are expected to enter the pleas at the military commission at Guantanamo Bay, Cuba, as soon as next week. Pentagon officials declined to immediately release the terms of the plea bargain.