Critics argued the president was inconsistently setting an "arbitrary" deadline while also claiming any transfer of responsibility to the Afghan government ultimately will be based on conditions on the ground in that country.
Obama's blueprint faced questions Wednesday as Secretary of State Hillary Clinton, Defense Secretary Robert Gates and Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, appeared before the Senate Armed Services Committee.
Announcing a firm date for starting an American withdrawal while also saying such a withdrawal depends on conditions on the ground "are two incompatible statements," said Sen. John McCain of Arizona, the committee's ranking Republican.
"You either have a winning strategy ... and then once it's succeeded, then we withdraw or, as the president said, we will have a date [for] beginning withdrawal in July 2011. Which is it? It's got to be one or the other. It's got to be the appropriate conditions, or it's got to be an arbitrary date. You can't have both."
Updated: 5: 00 p.m.