Susan Rice to replace Donilon as Obama's national security adviser WASHINGTON, June 5 (Xinhua) -- U.S. National Security Adviser Tom Donilon had resigned and would be replaced by U.N. ambassador Susan Rice, U.S. media reported Wednesday. The Washington Post quoted senior administration officials as saying President Barack Obama would make a formal announcement later in the day, and the resignation would take effect early next month. The report credited Donilon with executing the administration's shift to a stronger focus on Asia in its foreign policy, adding his resignation was timed to follow the summit meeting he helped organize between Obama and Chinese President Xi Jinping this weekend. Other reports said Donilon, 58, a low-key veteran Washington insider known for his long work hours, was exhausted and eager to spend more time with his ailing wife, after serving more than four years with the administration, first as deputy national security adviser, then in the top job. Obama is expected to nominate Samatha Power, who served as an aide at the National Security Council during Obama's first term, to replace Rice at the United Nations.