President George W. Bush will nominate the U.S. ambassador to Russia, William Burns, to take the State Department's third-highest job, senior U.S. officials told The Associated Press on Friday. He would replace Undersecretary of State for Political Affairs Nicholas Burns, whose resignation Secretary of State Condoleezza Rice announced Friday. William Burns was previously the top U.S. diplomat for the Middle East. The two men are not related. The officials who confirmed that William Burns would be appointed spoke on condition of anonymity because the formal announcement had not been made.