American diplomat Richard Holbrooke critically ill

Mr Holbrooke, 69, named special envoy for Afghanistan and Pakistan when President Barack Obama took office in 2009, earned a reputation as a "bulldozer" in helping negotiate the 1995 accord that ended the Balkans war.

"This morning, doctors completed surgery to repair a tear in his aorta," said a statement from the State Department. "He is in critical condition and has been joined by his family."

Shortly after graduating from Brown University in 1962, Mr Holbrooke was working for the State Department in Vietnam and was an aide at the Paris peace talks.

He was a top foreign policy adviser to Hillary Clinton in her failed presidential bid in 2008. After Mr Obama won the Democratic nomination, Mr Holbrooke served as one of his advisers.

He has been nominated for the Nobel Peace Prize seven times and is the author of To End A War.

The diplomat, who also served as the US ambassador to the United Nations and to Germany and twice was assistant secretary of state, fell ill at the State Department on Friday and was taken to the hospital.

The aorta is the body's biggest artery, which are vessels that transport blood away from the heart to other parts of the body.