Iran's nuclear program was "definitely on the route for a bomb", but has been delayed by US strikes. an Australian nuclear expert says, but it will now be difficult to trace the enriched uranium.

Israel, joined by the United States on the weekend, has carried out attacks on Iran's nuclear facilities, after alleging Tehran was getting close to obtaining a nuclear weapon.

Iran denies ever having a nuclear weapons program, but Supreme Leader Ali Khamenei has said that if it wanted to, world leaders "wouldn't be able to stop us".

Australian National University's Department of Nuclear Physics and Accelerator Applications Honorary Associate Professor Tony Irwin said he believed Iran was "definitely on the route for a bomb".

"They've (Iran) tried to say for peaceful purposes, but you don't enrich up to 60 per cent for peaceful purposes," Irwin said.

The US strikes have destroyed the centrifuges, research centre and nuclear facilities, making it difficult for Iran to make more enriched uranium, Irwin said.
"But they might still have... ten bombs worth could be available and it's going to be very difficult to know," Irwin said.

While the enriched uranium can be transported, Irwin added that having the enriched uranium did not mean that Iran had a weapon.

"You've then got to do a deconversion from UF6 to uranium metal. So you need a plant to do that. And then you've got to have a delivery system. You've got to have a bomb design, and then a delivery system for the bomb as well. And if you're going to try and get it down to a size, you can put on a missile. You need quite advanced technology to be able to do that," he said.

The United States dropped the biggest conventional bombs in its arsenal on Iranian nuclear facilities over the weekend, using bunker-busting munitions in combat for the first time to try to eliminate sites including the Fordow uranium-enrichment plant dug into a mountain.

The International Atomic Energy Agency has not been able to carry out inspections in Iran since Israel started its military strikes on nuclear facilities there on June 13.

'Where's the 400kg (882 pounds)?' - Australian nuclear expert says Iran could have 'spirited away' its supply of enriched uranium. - Reuters