Because of his reputation of confronting the warring leaders in the Balkans to get them to the negotiating table, Mr Holbrooke was dubbed "the Bulldozer" or sometimes "Raging Bull" in the region.

But his most recent mission in the region - attempting to persuade Yugoslavia's President Milosevic to back down over Kosovo in the Spring - was a failure.

War zone veteran

Mr Holbrooke, 58, 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.

His first assignment for the state department was in Vietnam during the Indo-China wars. He later headed the State Department's European and Asian bureaux.

He has served as a former ambassador to Germany, and an assistant secretary of state for European affairs. In that post, he went to Bosnia as part of a peace-seeking delegation.

Since Dayton, he has worked as an investment banker, and part-time as a US envoy.

He is credited with averting a possible military confrontation between Greece and Turkey over a disputed in the Aegean Sea.

He again met delegations of both governments at the negotiating table, trying to push forward the peace process on the Mediterranean island of Cyprus. This mission did not end in success.

In 1998 President Bill Clinton nominated Mr Holbrooke as the next US ambassador to the United Nations but it took the Senate 14 months to confirm him in this job.

Getting along with Milosevic

Over the course of their various protracted and often difficult negotiations, Mr Holbrooke has established something of a rapport with the Yugoslav President, Slobodan Milosevic. The two men are said to be on a first name basis.

On a first name basis

There are stories of Mr Holbrooke sipping a mid-morning pear brandy with Mr Milosevic at Dayton, and the Yugoslav President once hosted the US diplomat for an 11-hour dinner near Belgrade at the former hunting lodge of the long-time Yugoslav President Tito.

The two men went for long walks in the woods around the time of the late-summer 1995 Nato airstrikes in Bosnia, which Mr Holbrooke heartily endorsed even as Mr Milosevic tried to soften up the native New Yorker, saying he loved the smell of coffee in Manhattan.

Mr Holbrooke says he has no moral qualms about "negotiating with people who do immoral things".

"If you can prevent the deaths of people still alive, you're not doing a disservice to those already killed by trying to do so," he said this summer after he failed to persuade Mr Milosevic to stop his military assault on ethnic Albanians in Kosovo.

"And so I make no apologies for negotiating with Milosevic and even worse people, provided one doesn't lose one's point of view."

The Kosovo crisis saw him back in Belgrade, trying to persuade President Milosevic to withdraw his troops from the province.

Mr Holbrooke with Secretary of State Madeleine Albright

This mission failed, but that was not enough to ruin Mr Holbrooke's reputation as one of the best and toughest US diplomats.

He is also known to have enemies in the US government.

In 1997, he was widely tipped to become secretary of state, but lost out to Madeleine Albright.

When Mr Holbrooke takes up his post at the UN, analysts in Washington will be keen to spot any signs of rivalry with Mrs Albright.