Iran could gain the capability to make a nuclear weapon in 2-5 years but there is ample time to deal with the concern, the head of the United Nations' nuclear watchdog said in a televised interview.

Mohamed ElBaradei, director-general of the Vienna-based U.N. International Atomic Energy Agency (IAEA), said that after stockpiling enriched uranium, Iran would face further technical and political hurdles should it seek to build nuclear arms.

"There is a concern, but don't hype the concern," ElBaradei, alluding mainly to U.S. and Israeli warnings, said in a CNN interview broadcast late on Sunday. "There is ample time to engage (Iran) and reverse the concern and to move into more engagement rather than more isolation."

ElBaradei said that for Iran to have weapons capacity, it would have to eject IAEA inspectors, leave the Non-Proliferation Treaty (NPT), reconfigure production to refine uranium to the high degree needed for bomb fuel and fit the material into a warhead:

"Even if I go by the CIA and other U.S. intelligence, the estimations (are) that if even if they go through all these scenarios, we're still talking about two to five years from now."

Western powers believe Iran's declared programme to refine uranium to the low level required for civilian nuclear energy is a front for gaining the means to reprocess it into highly enriched material for bombs at short notice.

Iran insists its nuclear ambitions are limited to the peaceful generation of electricity, and refuses to freeze a programme that it says is its sovereign right under the NPT.

It is under IAEA investigation over alleged military dimensions to its nuclear work as well as U.N. sanctions imposed over past undeclared activity and a failure to prove its nuclear intentions are wholly peaceful.

The IAEA's last report on Iran in November said it planned to start installing another unit of 3,000 enrichment centrifuges in early 2009, adding to 3,800 machines already enriching uranium and another 2,200 being gradually introduced.

Some Western analysts believe Iran will have enriched enough uranium by later this year to make a bomb if it wishes. Iran says it will enrich uranium only to the low level needed for civilian power.

In an interview with the Washington Post, ElBaradei said Iran had seen that the ability to build an atom bomb in a short period would give it an insurance policy against attack.

"Obviously, they look for their own security, and they have seen that if you have nuclear weapons, or at least the technology, you are somehow protected from an attack," he told the Post's Sunday edition.

ElBaradei urged Iran anew to cooperate with the IAEA probe in order to build trust, but also blamed the impasse on the Bush administration, which declined to open a dialogue with Iran.

He praised new U.S. President Barack Obama for being willing to start direct dialogue with Iran without preconditions.