President Barack Obama plans Wednesday to announce the resignation of Tom Donilon as national security adviser, one of his closest aides, with ambassador to the UN Susan Rice. No reasons were offered for the surprise shakeup in the president’s inner foreign policy circle. Republican pressure forced Rice, 48, to withdraw from the running as foreign secretary over her statements on the Benghazi attack in which al Qaeda murdered four US diplomats. John Kerry took her place. Her appointment, which does not require Senate approval, will strongly antagonize the Republican side of the house.