United Nations ? Secretary-General Kofi Annan’s biggest regret of his nine-year tenure was not being able to prevent the war in Iraq, the U.N. chief said Wednesday during his annual year-end news conference.

The United Nations’ inability to head off the U.S.-led invasion in 2003 “still haunts me and bothers me,” he said, because it caused lasting divisions that still trouble the world body today.

He said he had intervened personally with officials from many nations to try to head off the invasion, and wished that U.N. inspectors seeking to establish whether Iraq possessed weapons of mass destruction had been given more time to work. “But we were not able to do that,” he said.

Annan has tried in the past to appear assiduously neutral on the subject of the Iraq war, despite one slip during a British Broadcasting Corp. interview in which he declared the war “illegal.”

As he enters the final year of his term, Annan on Wednesday exposed facets of his personality rarely seen in public, alternately combative, wistful, hopeful and bitter.

“The year about to end has been a really difficult one,” he said, citing the tsunami that struck Southeast Asia at the end of 2004, continuing conflicts in the Middle East and Africa, and the U.N. oil-for-food scandal that sparked calls for his resignation.

“Let us look forward to what we can and must do next year,” he said, “and what we have to build on.”

Annan said he would focus on three priorities during his final year: fighting against poverty; promoting peace and security; and reforming the world body.

He said he would tell his successor that it is easier to give advice than to take it, and urged his replacement to have “thick skin and a sense of humor.”

Moments after that, Annan revealed the reason why. He lashed out at reporters for their “obsessive” pursuit of the oil-for-food scandal, which exposed corruption in the U.N.-led program that allowed former Iraqi leader Saddam Hussein’s regime to sell oil despite an embargo. Annan hoped the U.N. would “never be asked to take on a program like that again.”

While the effects of the oil-for-food scandal are likely to follow him, Annan said he hoped that his ultimate legacy would be a revitalized institution.

“If there’s one thing I would like to hand over to my successor when I leave office next year, is that it should be a U.N. that is fit for the many varied tasks and challenges we are asked to take on today,” he said.