President George W. Bush's special envoy for Sudan, Andrew Natsios, resigned on Friday and was replaced by a former US diplomat to the United Nations amid questions about the administration's policies toward the vast African nation. Also Friday, the State Department's top diplomat for refugee crises announced her imminent departure. Ellen Sauerbrey, the Assistant Secretary of State for Population, Refugees and Migration, who has been criticized for the handling of Iraqi refugee admissions, said she would be leaving the post soon. By law, Sauerbrey, a former Republican politician whom Bush named as a "recess appointment," bypassing a tough fight for Senate confirmation, cannot stay in the position after Congress returns in mid-January from its holiday break unless she is re-nominated and confirmed. "It has been a great privilege," she said in a farewell e-mail obtained by The Associated Press.