US secretaries of state have wielded various degrees of influence during their time at the top. We look here at some of the most memorable in recent history.
Served: 1973 - 1977
Famous quote: "Power is the ultimate aphrodisiac"
Henry Kissinger was both secretary of state and national security adviser under President Richard Nixon, and as such wielded immense influence on the shape of US foreign policy in the 1970s.
Henry Kissinger (R) wore two hats under Nixon
It was Mr Kissinger who negotiated the ceasefire agreements ending US involvement in the Vietnam War, for which he won the Nobel Peace Prize. His secret meetings paved the way for Richard Nixon's groundbreaking visits to Beijing and Moscow. He also brokered a peace treaty between Israel and Egypt.
But he remains a controversial figure, particularly over his complicity in the illegal carpet-bombing of neutral Cambodia and America's role in the 1973 coup which brought down Chile's Allende government and ultimately set up the military regime of Gen Augusto Pinochet.
Served: 1982 - 1989
Famous quote: "In Washington, it is never over till it is over, but this is Washington, therefore it is never over"
George Schultz was secretary of state during the Reagan administration and is seen as an important figure in the final years of the Cold War.
George Schultz clashed with the then Defense Secretary Weinberger
His relationship with Defense Secretary Caspar Weinberger was widely seen as tempestuous, and the two are thought to have clashed regularly on policy toward the Soviet Union, but with little long-term impact on policy.
Served: 1989 - 1992
Famous quote: "Never let the other fellow set the agenda"
As George HW Bush's secretary of state, much of Mr Baker's focus was on the Middle East and the collapsing Soviet Union.
Baker was seen at the time as presidential material
He was a distinguished and shrewd operator, especially with regard to his relations with his Soviet counterpart, Eduard Shevardnadze, during the climactic years of the end of the Cold War. On that front, he helped the United States reach agreement with the Soviet Union on the unification of East and West Germany in 1990.
In 1990-91 he was instrumental in orchestrating the international coalition that opposed Iraq's invasion of Kuwait. He resigned his post as secretary of state in 1992 in order to serve as White House chief of staff while simultaneously directing Mr Bush's unsuccessful re-election campaign.
Served: 1997 - 2001
Famous quote: " I was a little girl in World War II and I'm used to being freed by Americans"
America's first female Secretary of State Madeleine Albright served under President Bill Clinton. Trained as an academic, rather than as a career diplomat, she soon established a reputation for bluntness, especially where human rights violations or US interests were concerned.
Albright was a key proponent of action in the Balkans
It was in this human rights context that she became an ardent supporter of military intervention in the Balkans, although she was widely lambasted in 1996 for appearing to suggest in a television interview that the sanctions against Iraq were worth the deaths of thousands of children.
She was a busy foreign secretary who frequently travelled far and wide.
Served: 2001 -
Famous quote: "Either move or be moved"
The first African-American to hold that position, Colin Powell was seen throughout his four years as the moderate voice of the Bush administration.
He became marginalised in Washington during the build-up to the war in Iraq in the second half of 2002. He was the most influential proponent of seeking a UN mandate for action against Iraq, and his most memorable moment was his presentation to the Security Council on 5 February 2003, in which he produced satellite images and recordings supposedly showing Iraqi attempts to conceal banned weapons.
Colin Powell resigned from his post
America never gained UN approval for the war, and it now seems unlikely that the weapons in question existed when the invasion was launched.