United Nations ? Sergio Vieira de Mello, a diplomatic veteran who served for more than 30 years as a troubleshooter in world hot spots and became the top U.N. envoy in Iraq, was killed Tuesday in a truck bombing against his offices in Baghdad. He was 55.

A rising star within the world body, the Brazilian envoy had been talked about as a future secretary-general.

After being named to the Iraq post in June, the diplomat said his top priority was to protect the interests of the Iraqi people under the U.S.-led occupation.

“I have been sent here with a mandate to assist the Iraqi people and those responsible for the administration of this land to achieve … freedom, the possibility of managing their own destiny and determining their own future,” he said on arrival in Baghdad.

In a briefing to the U.N. Security Council just 3 1/2 weeks ago, he warned that security in Iraq remained tenuous.