Washington: The US Senate voted 100-0 to confirm FBI Director Robert Mueller to two more years at the head of the country's elite crime-fighting and counter-terrorism force.

The move came on Wednesday, a day after President Barack Obama signed a law allowing him to serve two years beyond the statutory 10-year limit.

Mueller, nominated by ex-President George W. Bush in July 2001, took over the Federal Bureau of Investigation a week before the September 11 attacks, which led to a global anti-terror campaign that has dominated his tenure.

The previous procedure for nominating FBI Directors and limiting their tenure to 10 years was brought in around the death in 1972 of the powerful J. Edgar Hoover, who had maintained an iron rule in the post for 48 years.

Hoover, who was the first FBI Director, was credited with building up the bureau as a crime-fighting agency, but became a controversial figure accused of harassing political activists and amassing secret files on political leaders.

Mueller has faced criticism from civil liberties groups over alleged abuse of broad intelligence and surveillance powers the US Congress granted the FBI in the wake of the September 11th attacks. He has denied overstepping his bounds.