U.S. President Barack Obama has awarded retiring Defense Secretary Robert Gates the Presidential Medal of Freedom.

President Obama presented the medal to Gates at an armed forces farewell tribute Thursday, Gates' last day as defense chief.

Mr. Obama called Gates one of the nation's finest public servants and one of the best defense secretaries in U.S. history.

Gates became head of the Pentagon in late 2006 under President George W. Bush, and oversaw a troop surge in Iraq that analysts say helped turned the campaign around.

Gates said serving as secretary of defense has been the greatest honor and privilege of his life. He is the only defense chief in U.S. history to be asked to remain in the post by a newly-elected president.

In a farewell message to U.S. forces Wednesday, Gates thanked service members and their families, saying their dedication and courage has kept America safe. He said their efforts brought the war in Iraq to a successful end and are “turning the tide” in Afghanistan.

Leon Panetta, formerly the head of the U.S. Central Intelligence Agency, is succeeding Gates as defense secretary.

Panetta has said his first task at the Pentagon will be to ensure the U.S. prevails in the conflicts it is engaged in, including in Iraq and Afghanistan.

Gates leaves as the U.S. prepares to drawn down its forces in Afghanistan, with 10,000 troops leaving this year and another 23,000 by September 2012.