NEW YORK - Former United States President Bill Clinton's first Secretary of State, Warren Christopher, has died at the age of 85 after a career of quiet heroism in which he helped bring peace to the Balkans and resolve the Tehran hostage crisis through dogged negotiation.

Christopher, who died at home in California after suffering from bladder and kidney cancer, was the venerable establishment figure to Clinton's boyish rogue when he was invited, aged 68, to become Secretary of State in 1993.

Hillary Clinton, Secretary of State now, paid tribute to the man who came to be known as her husband's "dog of peace" in his efforts to thrash out the 1995 Dayton agreement to end the Bosnian War.

"Warren was a diplomat's diplomat, talented, dedicated and exceptionally wise," said Clinton.

President Barack Obama said he mourned the passing of a man who proved to be a "resolute pursuer of peace" and dedicated public servant.

"Warren Christopher was a skilful diplomat, a steadfast public servant, and a faithful American," the President said.

"In a quiet and effective way, he had many momentous achievements in his life of dedicated service," said former President Jimmy Carter, whose administration oversaw the hostage crisis. Christopher secured the release of the 52 American hostages held for more than a year in the embassy in Tehran after the Iranian revolution in 1979.

In 2002, he accused President George W. Bush of having "a fixation on attacking Iraq" and urged that he turn his attention instead to the greater threat of North Korea.

He set a new record for the number of air miles clocked up by a secretary of state over a four-year period.

By October 1996, he had flown 704,487 miles (1,133,762km).

The lawyer turned envoy tirelessly travelled to Bosnia and the Middle East on peace missions during his 1993-1996 tenure - including two dozen to Syria alone in a futile effort to promote a settlement with Israel.

Along with his peace efforts, he said his proudest accomplishments included playing a role in promoting a ban on nuclear weapons tests and extension of curbs on proliferation of weapons technology.

The loyal Democrat, who went back to his law firm, also headed Clinton's vice-presidential search committee, recommending Al Gore for the party's 1992 presidential ticket, and he also supervised the contested Florida recount for Gore in the 2000 presidential election. The Supreme Court, on a 5-4 vote, decided for George W. Bush.