VIENNA (Reuters) - Iran is unlikely to be able to make atomic bombs before 2013, a former senior official of the U.N. nuclear watchdog said on Wednesday, dismissing suggestions it could happen in months if Tehran decided to pursue such mass-destruction weaponry.
Olli Heinonen, head of U.N. safeguards inspections worldwide until last year, said he believed Iran would need a couple of years to develop a capability to manufacture nuclear-armed missiles, based on what is now known about its activities.
"Then you still have to build them and that will take time. I don't think it is immediate," Heinonen told Reuters. "But Iran certainly has the elements in place and has built up its capabilities."
Iran says its nuclear program is for peaceful electricity generation, rejecting Western accusations it is enriching uranium for the ultimate purpose of atomic bomb fuel.
Heinonen, now a senior fellow at Harvard University's Belfer Center for Science and International Affairs, said Iran was on the "way to no good" with its nuclear work but it did not appear to have taken a political decision yet to actually build bombs.
Refined uranium can be used to fuel nuclear power plants, Iran's stated goal, or provide material for bombs if processed much further.
Estimates on when the Islamic state could assemble atomic weapons, if it wanted to, are significant as they could determine how much time the major powers have in trying to resolve the long-running nuclear dispute diplomatically.
U.S. defense analyst Greg Jones delivered one of the more urgent warnings last month, arguing that if Iran decides to make a nuclear weapon it could produce enough highly-enriched uranium (HEU) in about eight weeks.
Iran "needs to be treated as a de facto nuclear power simply by virtue of being so close to having a weapon," Jones, of the Nonproliferation Policy Education Center, said in an article in U.S. political magazine New Republic.
Other experts say such estimates are unrealistic, given the technical hurdles Iran must still overcome.
"Maybe by the end of next year they might have enough material to do it but then to turn it into weapon-grade level (in view of the low performance of its current IR-1 centrifuge machines) takes another half year at least," Heinonen said when asked about a timeline for any Iranian weapons bid.
The Islamic Republic's refusal to halt its enrichment activities has drawn four rounds of U.N. sanctions since 2006.
Even if Iran were to produce bomb-grade uranium, it would also have to transform it from gaseous into metal form, miniaturize the material to squeeze into the nose cone of a missile, and fit the device with a trigger system.
"They work in all three areas -- enrichment, nuclear device design and a missile system to deliver -- and in all areas probably progress is slow but you need to have all of them in place in order to have the weapon," Heinonen said.
"I think they are now focusing on having the most important part, the fissile material, available if they want to do it."
Sanctions and possible sabotage -- such as the Stuxnet computer virus and recent killings of nuclear scientists that Tehran blames on Israel -- may have slowed Iran's atomic advance.
But its stockpile of refined uranium is steadily growing and experts estimate Iran now has enough low-enriched material for at least two bombs, if the material is refined much more.
Israel and the United States, Tehran's arch foes, have not ruled out military action if diplomacy fails to resolve the row. Israel bombed an Iraqi reactor in 1981 and launched a similar sortie against Syria in 2007.
Mark Fitzpatrick, a director of the International Institute for Strategic Studies think-tank, said this week that it would make no sense for Iran to risk air strikes unless it could produce at least a handful of weapons.
Heinonen agreed: "Who breaks out with one? Only a madman."
Editing by Mark Heinrich