"I think resignation is comparatively easy. It is much more difficult to stay on and continue to do the job you are elected to do, and focus on the important agenda of the organisation and the membership," he said in an interview to the Financial Times published Monday.

Annan's son profited from Iraq

New revelations concerning about payments to his son Kojo in the UN's supervision of Iraqi oil sales under Saddam Hussein's regime has sparked off a controversy with some US senators like Norm Coleman, who is leading a congressional probe, calling for his resignation.

"My hope had been once the independent investigative committee had been set up, we would all wait for them to do their work, and then draw our conclusions and make judgements. This has not turned out to be the case for some who have been relentless in their attacks," the secretary general said.

Asked why he was being targeted, Annan said, "There are those who believe that the organisation has not been helpful in recent times. There may be other reasons, and as Secretary general, I'm the face of the organisation, so I'm the obvious target."

When asked how it affected him personally, Annan said, "Obviously it's difficult for me as Secretary General of the UN and as a father. But we need to continue with our work."