Vienna: 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.

Mohammad Al Baradei, director-general of the Vienna-based UN 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," Al Baradei, alluding mainly to US 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."

Al Baradei 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 US intelligence, the estimations [are] that 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 for peaceful purposes.