Washington, June 22 (IANS/EFE) The US Senate voted unanimously Tuesday to confirm CIA Director Leon E. Panetta as the next secretary of defense, replacing Robert Gates.

Panetta, who last week received a unanimous endorsement from the Armed Services Committee, became President Barack Obama's first Cabinet nominee to win Senate approval by a vote of 100-0.

The veteran Washington hand promised the committee to closely monitor the Pentagon's modernisation efforts.

Among the challenges facing Panetta will be managing the gradual withdrawal of US forces from Afghanistan, implementing a proposed $400 billion reduction in planned future military spending and directing military operations in Libya.

He will also preside over the end of the military's Don't Ask, Don't Tell policy, which forced gay and lesbian service personnel to conceal their sexual orientation.

Another task for the new Pentagon boss is overseeing the US withdrawal from Iraq at the end of this year.

Panetta, who represented California in the House of Representatives from 1977 to 1993, served successively as director of the Office of Management and Budget and White House chief of staff under President Bill Clinton.

Obama has nominated Gen. David Petraeus, until now the commander of NATO forces in Afghanistan, to succeed Panetta as CIA chief. The general's confirmation hearing before the Senate Intelligence Committee begins Thursday.