U.S. Defense Secretary Leon Panetta is a former Democratic congressman with a long history in the U.S. government and extensive budget experience.

The chief of the Central Intelligence Agency until he was named to run the Pentagon, Panetta headed the White House budget office under President Bill Clinton and also served as chairman of the House of Representatives Budget Committee for four years.

Panetta's budget skills will be put to the test as President Barack Obama has called for an additional $400 billion in cuts to security spending. The 72-year-old Panetta will have to balance that with national security needs and the challenge of U.S. military involvement in Iraq, Afghanistan and Libya.

Panetta was elected to his first of eight terms in the U.S. House of Representatives in 1976, representing a district in California.

He is credited with bringing Congressional connections and cohesion to the CIA, which he took over in 2009.

In the 1990s, after heading the White House budget office, Panetta also served as chief of staff to President Clinton.

Following a stint as an Army intelligence officer, Panetta started out his political career working for Republicans, eventually becoming head of the Office for Civil Rights under President Richard Nixon. He left the post because of a disagreement and switched to the Democratic Party in 1971.