Mr Cyrus Vance, a former US Secretary of State who resigned over the botched 1980 attempt to save US hostages in Iran, has died aged 84.
Mr Vance, who had Alzheimer's disease, was a patient at the Mount Sinai Hospital in New York.
As secretary of state for former President Jimmy Carter, Mr Vance helped fashion the 1979 peace treaty between Egypt and Israel.
He sought to secure a permanent arms-control agreement with the Soviet Union, helped normalise US relations with China and helped gain approval for treaties on the Panama Canal.
But in April 1980, President Carter approved a military operation to rescue hostages seized the previous year at the US embassy in Tehran. Mr Vance so strongly opposed the idea that he resigned - and the rescue attempt ended in spectacular failure.
Mr Vance was one of the few senior US officials ever to step down on a point of principle. Three years ago Mr Vance urged the United States and Iran to resume diplomatic relations.
In 1991, then-UN Secretary General Javier Perez de Cuellar appointed him as negotiator in the former Yugoslavia.
He was part of a team that won a ceasefire between Serbs and Croats in Croatia but resigned in 1993 after failing to end the fighting in Bosnia.