Outgoing United Nations Secretary-General Kofi Annan on Tuesday told the nuclear weapon powers that they cannot tell others not have atomic arms if they themselves keep and upgrade their own arsenal.

If the nuclear weapon states take the plea that they need them for their own defence, they cannot tell the non-nuclear weapon states that they don't need them for the same purpose, he said.

Replying to a question about the suspected ambition of Iran to produce nuclear weapon in the context of Israel declaring that it has such arms, Annan said that India, Israel and Pakistan have not signed the Nuclear Non Proliferation Treaty and hence are not under that pressure.

But Iran, having signed the treaty, needs to abide by the obligations it has undertaken, he told his last press conference before he hand over the reins of the organisation to the new incumbent Ban Ki-moon on January 1, 2007.

But he agreed that Israel admitting that it has nuclear weapons would have an effect in the region as several countries say they are looking to produce nuclear power.

Without saying that American led invasion of Iraq was illegal as it not had the backing of the Security Council, Annan told reporters that where broader international threats are concerned, the Security Council's approval give legitimacy to such an action.