He then became acting director for European and Eurasian Affairs for the National Security Council. In that capacity he was in charge of US preparations for 2004 Istanbul summit of NATO members and the 2002 Prague summit. In July 2005, Volker became the Principal Deputy Assistant Secretary of State for European and Eurasian Affairs, serving in that position until he was appointed United States Permanent Representative to NATO in July 2008 by President George W. Bush. Volker served as Ambassador in that position from July 2, 2008, to May 15, 2009.