Comings and goings: Arms control

Moves afoot in the Obama White House arms control shop: National Security Council non-proliferation hand Rexon Ryu has begun work as the deputy to the U.S. representative to the United Nations, heading up the US/UN's Washington office. Ryu, a former staffer to former Sen. Chuck Hagel (R-Neb.), met with Deputy Secretary of State Thomas Nides about his new appointment last month, according to Nides' public schedule. Ryu succeeds Erica Barks-Ruggles, who is off to South Africa to serve as the consul general of the U.S. consulate in Cape Town.

Succeeding Ryu as an NSC director for non-proliferation: the State Department's Jofi Joseph. Joseph, currently senior adviser to Under Secretary of State for Arms Control Ellen Tauscher, previously served as a non-proliferation expert on the staff of the Senate Foreign Affairs Committee and for Sen. Robert Casey (D-Penn.). At the NSC, Joseph's portfolio will focus on Iran and North Korea, reporting to White House WMD czar Gary Samore.

Also joining Samore's shop: Lynn Rusten, a former Senate Armed Services Committee staffer who recently played a key role at State in the negotiations on the New START Treaty under Assistant Secretary Rose Gottemoeller. Rusten succeeds Anita Friedt, who has returned to the State Department.