Annan defends UN as 'vital to humanity'

"I have served the UN all my life. I have done, and am still doing, everything I can to correct its imperfections, and to improve and strengthen it," he wrote in an opinion piece. "And I believe profoundly in the importance of that task, because a strong UN is of vital importance to humanity."

Annan addressed charges of mismanagement and corruption in the UN's now-defunct Iraqi oil-for-food program, admitting there were failings while accusing some critics of hyperbole.