LOS ANGELES — Former secretary of state Warren Christopher, a "diplomat's diplomat" who helped negotiate peace in the former Yugoslavia and advanced the Middle East peace process, has died at the age of 85, officials said.

He had reportedly been suffering from kidney and bladder cancer.

A lawyer by training, Christopher served for four years as secretary of state in the administration of former president Bill Clinton, who appointed him to the job in 1993.

"Warren was a diplomat's diplomat -- talented, dedicated and exceptionally wise," Secretary of State Hillary Clinton said in tribute to her friend and predecessor.

"As well as anyone in his generation, he understood the subtle interplay of national interests, fundamental values and personal dynamics that drive diplomacy," she said.

During his tenure he focused on expanding the NATO alliance, establishing peace between Israel and its neighbors, and ending the war in Bosnia-Herzegovina.

He was instrumental in consolidating the Oslo Accords between Israel and the Palestinians, the Dayton Agreement that ended the war in Bosnia, and helping to uphold democracy in Haiti.

After Israel and the Palestinian secretly negotiated the Oslo Accords, which created the Palestinian Authority in exchange for Palestinian recognition of Israel's right to exist, Christopher was chosen to host the signing ceremony.

The ceremony took place in Washington in September 1993, with Yasser Arafat signing for the Palestine Liberation Organization and Prime Minister Yitzhak Rabin signing for Israel.

Following the signing, Christopher encouraged Jordan's late King Hussein to draw up a peace treaty with Israel, similar to the one that existed between Israel and Egypt.

That accord, seen as one of the major achievements in Middle East peace diplomacy was signed by Israeli and Jordanian leaders in October, with Christopher and then-president Clinton witnessing the ceremony.

Another crowning achievement of the late US secretary of state was negotiating a successful conclusion of the Bosnia's 1992-1995 war which cost an estimated 100,000 to 110,000 lives.

In addition, over 2.2 million inhabitants were displaced as a result of the strategy of "ethnic cleansing" adopted by former Serb leaders, which made it the most devastating conflict in Europe since the end of World War II.

With the late special envoy Richard Holbrooke as his point man, Christopher helped launch peace talks between then-presidents Slobodan Milosevic of Serbia, Franjo Tudman of Croatia and Alija Izetbegovic of Bosnia.

The secret talks resulted in the signing in November 1995 of the Dayton peace agreement, which -- albeit with multiple setbacks -- helped end the Bosnian war.

Christopher also helped spearhead in 1994 Operation Uphold Democracy, during which a US-led coalition returned Haiti's popularly-elected President Jean-Bertrand Aristide to power after he had been ousted by a coup.

Aristide, Haiti's first democratically-elected leader, made another triumphant return home from exile just on Friday, two days before a presidential run-off election.

After leaving government service, Christopher dedicated himself to practicing law in California and teaching international affairs at the University of California in Los Angeles.

He also served as an honorary co-chairman of the World Justice Project, a program aimed at promoting the rule of law and community development.