One of America's most prominent diplomats, Richard Holbrooke, is critically ill.
Mr Holbrooke, 69, was admitted to hospital on Friday and has undergone surgery to repair a tear in his aorta.
The BBC reports his family are at his bedside in Washington DC.
Mr Holbrooke was at the State Department when he was taken ill. The aorta carries oxygenated blood from the heart.
Mr Holbrooke is best known for brokering the Dayton peace accords in 1995, which ended the Bosnian war. He also served in Vietnam and at the United Nations.
In the wake of his success at Dayton, he was nominated for the Nobel Peace Prize.
President Barack Obama named Mr Holbrooke as his special representative to Afghanistan and Pakistan in January 2009.
Since then, he has maintained a hectic travel schedule. In September, he visited Pakistan to see the aftermath of the floods there.
He has also travelled to the north-west Pakistan, a stronghold for insurgents.
The BBC reports Mr Holbrooke was born in New York and is of German-Jewish descent. He was educated at Brown University, and is married to the writer, Kati Marton.
As well as his diplomatic career, he has also worked in the financial sector.
