"If you tell the enemy that you're leaving on a date certain, unequivocally, then that enemy will wait until you leave," Sen. John McCain, R-Ariz., said Sunday on ABC's "This Week."
"I'm all for dates for withdrawal, but that's after the strategy succeeds, not before," said McCain, speaking from Afghanistan, where he's staying through the Fourth of July weekend.
"The president should state unequivocally that we will leave when we have succeeded."
Sen. Lindsey Graham, R-S.C., who was also in Afghanistan, said the July 2011 date has caused confusion and "emboldened" Taliban and al-Qaida militants.
"If people think we're going to leave, we have no chance of winning," Graham said on CBS's "Face the Nation."
"If you send a signal to your enemy you're going to leave at a certain date, they'll wait you out."
Still, he said he was hopeful some parts of Afghanistan could be turned over to Afghan forces in the coming year.
Graham said he had spoken to Vice President Joe Biden, and Biden told him withdrawal of any U.S. troops would be "conditions-based."
Said Tayeb Jawad, the Afghan ambassador to the United States, also criticized the date for beginning the pullout.
"If you overemphasize a deadline that is not realistic, you're making the enemy a lot more bold, you're prolonging the war," Jawad said on CNN's "State of the Union."
"That deadline should be realistic, that deadline should be based on the reality on the ground. And we should give a clear message to the enemy, to the terrorists who are threat to everyone, that the United States, NATO and Afghans are there to finish this job."