The Senate voted 94-0 to approve the nomination of Petraeus, who has been in charge of US and NATO forces in Afghanistan since June 2010. His predecessor Leon Panetta has been confirmed unanimously by the Senate as secretary of defense to succeed Robert Gates, who officially retired on June 30.

Petraeus has gained great esteem for successfully leading multinational forces in Iraq. He was one of the architects for a plan President Barack Obama announced late 2009 which called for a significant troop surge in the country before phased drawdown.

However, the general did not seem to fully agree with Obama on the newly unveiled plan to withdraw from Afghanistan, though he said he endorsed the president's decision.

"The ultimate decision was a more aggressive formulation, if you will, in terms of the timeline than what we had recommended," Petraeus said at his Senate confirmation hearing last week.