WASHINGTON - APRIL 08:  Democratic presidential hopeful Sen. Barack Obama (D-IL) looks over hisnotes while listening to testimony from U.S. Army Gen. David Petraeus, Commander of American forces in Iraq, and U.S. Ambassador to Iraq Ryan Crocker during a hearing of the Senate Armed Services Committe on Capitol Hill April 8, 2008 in Washington, DC. Petraeus told Congress that he does not recommend lowering the number of U.S. troops in Iraq below 140,000.  (Photo by Chip Somodevilla/Getty Images)