NEW YORK (AP) — Cyrus R Vance, who resigned as President Jimmy Carter’s secretary of state over an ill-fated attempt to save American hostages from Iran, died Saturday. He was 84.

Vance died at Mt Sinai Medical Centre after a long battle with Alzheimer’s disease, said his son, Cyrus R Vance Jr. He said he did not know the cause of death.

Heading the State Department was the highlight of Vance’s career, but his duties on behalf of presidents, the Congress and the United Nations spanned more than three decades. He used his peacemaking skills to ease conflicts in foreign lands, racially torn American cities and even corporate boardrooms.

“A champion for peace and human rights, he was a superb statesman, who served me and other presidents well,” Carter said in a statement from himself and his wife Rosalynn. “We will miss his friendship, and the world will miss his humanitarian work and goodness.”

Quiet and self-effacing, Vance was a study in contrasts with Henry Kissinger, his flamboyant predecessor at the State Department. Vance’s politics were far more liberal than Kissinger’s, and his political leanings often put him at odds with Carter’s national security advisor, Zbigniew Brzezinski.

Vance enjoyed several successes during his early period as secretary of state but suffered setbacks later on. He played a key role in normalising relations with China, winning approval for new Panama Canal treaties and helping negotiate a peace treaty between Egypt and Israel.

But Vance’s tenure also saw an expansion of Soviet influence in a number of areas, as well as the collapse of the pro-American monarchy in Iran and the seizure of American hostages in Tehran.

When Carter approved a military operation for the rescue of the hostages in April 1980, Vance resigned because he felt he could not support such a plan. His scepticism proved prescient; the operation ended in disaster.

Eight servicemen died when a Marine Corps helicopter crashed into a plane parked at a clandestine refuelling site in Iran. The 52 hostages became an issue in the 1980 presidential campaign and were held for 444 days before their release on Ronald Reagan’s inauguration day.

Vance Jr said his father acted on his own principles, whether the presidents he served agreed with him or not.

“My father believed if he held true to his principles the chips would fall where they may,” he said.

One of Vance’s most difficult diplomatic undertakings took place long after he left the State Department, when U N Secretary-General Javier Perez de Cuellar asked him in 1991 to try to end the fratricidal war in the former Yugoslavia. He helped achieve a cease-fire in Croatia but peace eluded him in Bosnia.

His strategy in Bosnia was the subject of considerable controversy. Vance felt strongly that negotiations were the only way to halt Serbian advances, rejecting critics who argued that his tactics amounted to appeasement of an aggressor.

He quit in despair after struggling with the Bosnian conflict for almost a year.

It wasn’t long before he plunged into an entirely different kind of peacemaking: resolving rival creditor claims involving a debt-ridden commercial real estate firm with extensive holdings in New York City. Vance helped the parties reach a settlement in July 1993.

Vance retired several years later, when Alzheimer’s disease began to curtail his activities, his son said Saturday.

“He was working full-tilt until he couldn’t anymore,” he said.

Cyrus Roberts Vance was born in Clarksburg, West Virginia, on March 27, 1917. After graduating with honours from Yale Law School in 1942, he entered the US Navy, serving as a gunnery officer in the Pacific during World War II.

A year after his discharge from the Navy in 1946, he married Grace Elsie Sloane, of a prominent family specialising in home furnishings. He joined the New York law firm of Simpson, Thatcher and Bartlett, with which he maintained a relationship for decades.

Vance entered civilian government service for the first time in 1957 when he served as special counsel for a Senate Armed Service sub-committee on preparedness.

Vance became general counsel for the Defence Department in 1961 during the Kennedy administration, working closely with then-Defence Secretary Robert McNamara.

He was appointed secretary of the Army in 1962, and in January 1964 President Johnson named him deputy secretary of defence. He became known in that role for his hawkish views on Vietnam.

During his three years of service as the No 2 figure at the Pentagon, Vance was dispatched by the White House on trouble shooting missions to Panama and the Dominican Republic.

He left the Defence Department for health reasons in June 1967 but agreed, at Johnson’s request, to go to Detroit to help assess the cause of race riots in the city. By November, he was leading a negotiating effort that helped head off a war between Greece and Turkey over Cyprus.

Over the next few months, he went on a peacekeeping mission to Korea and helped develop a peacekeeping plan for Washington D C following the death of Dr Martin Luther King Jr. During the last nine months of the Johnson presidency, Vance served as deputy chief of the U S delegation to the Paris peace talks.

Before Johnson left office, he presented Vance with the Medal of Freedom, the nation’s highest civilian award. “He has always placed his country before himself,” Johnson said of Vance. “He has served the United States with remarkable skill. He is a man of energy, uncompromising intellect and remarkable wisdom.”

In 1975, Vance and social scientist, Daniel Yankelovich, founded Public Agenda, a non-partisan, non-profit public opinion research and citizen education organisation based in New York City.

Vance is survived by his wife, five children and two grandchildren.