Sens. Robert Byrd (D-W.Va.) and Tom Harkin (D-Iowa) opposed the confirmation of Petraeus, while only Harkin opposed Odierno.

“You vote on nominations based on an individual’s qualifications,” said Sen. Blanche Lincoln (D-Ark.). “A difference of opinion doesn’t necessarily mean they’re not qualified.”

“The violence is marginally down in Iraq, but not enough to achieve our real goal, which is to bring American troops home,” added Majority Whip Dick Durbin (D-Ill.). “I don’t question Petraeus or Odierno in terms of their military service to our country. That’s not part of it. It’s the commander in chief that’s making the mistakes.”

But White House spokesman Tony Fratto said Petraeus and Odierno “have proven to be two of the finest military leaders in our nation’s history.”

“The president is confident that they are the best men to serve in these positions,” Fratto told reporters. “They will both do an excellent job in leading our troops to confront challenges in the war on terror and helping to keep our nation safe.”

Byrd’s office released a statement saying his vote against Petraeus’s confirmation reflects concern over constant turnover among U.S. commanders in Iraq, as well as Petraeus’s “unwillingness to address questions regarding other regional issues, such as in Afghanistan or Iran, during his confirmation hearing.”

Byrd also criticized the U.S. military's “stop-loss” policy, which he says is preventing 12,000 service members from leaving the service even though they have fulfilled their obligations.

“Sen. Harkin opposed these nominations because he does not believe that either Gen. Petraeus or Gen. Odierno will take us in the direction we need in Iraq, namely setting a timetable for redeployment of U.S. forces so that our country can begin to more effectively address the very real threat posed by terrorists around the globe,” said Harkin spokeswoman Jennifer Mullin.