Iran may need only a month to produce enough weapons-grade uranium for a nuclear bomb, a U.S.-based anti-proliferation group says in a new assessment of Tehran's enrichment program.
But that is only if the country were able to take the most extreme and direct enrichment path, says the Institute for Science and International Security in Washington. Under other scenarios, it would take significantly longer for Tehran to produce the material -- more than 11 months in one estimate.
And that would still not give Iran a nuclear bomb. Turning enriched uranium into a usable weapon would take a great deal more time, the report suggests.
The warning Thursday from ISIS was released as U.S. lawmakers consider legislation that could tighten sanctions on Iran until a deal is reached on the Middle Eastern country's nuclear program.
It also comes after talks resumed on the program between Iran and six world powers -- the United States, Russia, China, France, Germany and Britain -- known as the P5+1.
The report examines scenarios under which Iran could produce enough weapons-grade uranium to make a nuclear bomb -- and "break out" of the Nuclear Nonproliferation Treaty.
In a statement that described the report as "extremely alarming," House Majority Leader Eric Cantor, R-Virginia, urged the United States to consider all options, including the use of military force, "to prevent Iran from acquiring the world's most dangerous weapons. We all want negotiations to succeed, but time is clearly running out."
The report adds to the sense of urgency over the talks, said Shashank Joshi, a research fellow at the London-based Royal United Services Institute. But, he noted, not all analysts share the group's view. He said it would be difficult for Iran to secretly work toward a bomb without kicking out international inspectors.
ISIS appears to have overestimated the pace of Iran's nuclear development in the past, however. In a December 2008 report, it said Iran was expected to reach a nuclear weapons capability "during 2009 under a wide variety of scenarios."
The Iranian government declared the report baseless.
"This is a huge lie because, according to Iran's Supreme Leader Ayatollah Seyed Ali Khamenei, production, storage and use of weapons of mass destruction are haraam (forbidden by Islam)," said Marzieh Afkham, a Foreign Ministry spokeswoman. "Weapons of mass destruction have no place in the Islamic Republic's doctrine. This kind of report is totally false."
Important for negotiations
According to ISIS, the quickest route to a usable amount of weapons-grade uranium in the current circumstances could take Iran "as little as approximately 1.0--1.6 months."
It said it updated its estimates based on the view that Iran has increased the number of centrifuges at its Fordow and Natanz plants and has begun installing a more advanced centrifuge model at Natanz.
"The shortening breakout times have implications for any negotiation with Iran," the report says. "An essential finding is that they are currently too short and shortening further, based on the current trend of centrifuge deployments."
The U.S. government has said it believes Iran is about a year away from a nuclear weapon -- a more advanced stage than the one the ISIS report is forecasting.
ISIS says that its estimates don't factor in the time Iran would need to convert enriched uranium into weapons components and to build a nuclear missile.
"This extra time could be substantial, particularly if Iran wanted to build a reliable warhead for a ballistic missile," the report says. "However, these preparations would most likely be conducted at secret sites and would be difficult to detect."
Iran would face considerable hurdles to manufacturing a viable weapon without alerting International Atomic Energy Agency inspectors.
The inspectors frequently visit Iran's declared nuclear stockpiles -- sometimes with less than two hours' notice -- and check that Iranians are not carrying out other enrichment activities or diverting nuclear material, Joshi said.
"So if Iran was trying to bust the rules, it would not in two hours be able to conceal what it had been doing," he said.
Iran, whose economy is suffering severely under the U.S. and U.N. sanctions imposed because of its nuclear program, has long maintained that it is developing nuclear energy capabilities for peaceful purposes only.
But amid a tentative thaw in relations between Tehran and Washington since Iranian President Hassan Rouhani took office in August, Israeli Prime Minister Benjamin Netanyahu has urged the world community to be skeptical of Rouhani, calling him "a sheep in wolf's clothing."
And members from both parties in the U.S. Congress have urged the Obama administration not to prematurely loosen any of the sanctions on Iran's economy.