Analysts say a recently released International Atomic Energy Agency (IAEA) report makes it difficult for Iranian officials to claim their country's nuclear program is exclusively for peaceful purposes.
The IAEA has detailed how Iran has carried out computer simulations of nuclear explosions, worked on detonators and made more than a dozen designs for fitting atomic warheads to missiles.
"This report makes it pretty clear that Iran has weaponization in mind," says Matthew Kroenig, a Georgetown University expert on nuclear proliferation. "[Tehran is] doing the work they would need to do in order to make nuclear weapons, so it is harder for them to maintain the facade that this is purely a peaceful energy program."
The IAEA report does not say Iran has a nuclear weapon, but it says Tehran might have an ongoing weapons development program.
Such a claim, analysts argue, will increase international pressure on Tehran and alter dynamics of the Iranian nuclear issue. Britain, France and Germany have raised the possibility of additional sanctions on Tehran, but Russia and China - both permanent members of the United Nations Security Council - object.
Despite international opposition, the Iran is pressing forward with its nuclear programs, rejecting the report as a "fabrication" and accusing IAEA chief Yukiya Amano of being a "puppet" of the U.S. government. Tehran says information in the report came mostly from a laptop computer that was stolen from an Iranian official in 2004.
Valerie Lincy, editor of Iranwatch.org, calls the official denial inevitable.
"I think it is a more difficult position to take today ... because the IAEA has gone into great detail about the source of its information and the fact that this does not come from just one member state -- [i.e.], the United States," she says. "At this point the information is coming from a lot of different places, including the agency's own investigations."
A shared responsibility
Iran is not the only country challenged by the report's findings. Elliott Abrams, Deputy National Security Adviser for Middle East Affairs under President George W. Bush, suggests the new findings put the onus of how to address the issue on the shoulders of other nations.
"One effect of this report, I think, is that it does change the debate from the question of whether Iran is developing nuclear weapons to the question of what do we do about the fact that Iran is developing nuclear weapons," he says. "I think the IAEA report has kind of settled the first argument."
Security analyst Anthony Cordesman of the Center for Strategic and International Studies says the report raises questions of how long to continue negotiating with Tehran.
"At what point do you actually say, 'The military option has to be used or we have to decide to actually let them have a nuclear device,'" he says. "The problem, too, is that it is one thing to say that they might have a few devices, possibly over time, [but] it is another to let them go ahead and produce significant numbers of nuclear weapons."
The intellectual challenge
Middle East expert Ray Takeyh of the Council on Foreign Relations says international sanctions, and efforts to delay or disrupt Iran's nuclear program, are not working.
"We are increasingly no longer in management mode... the management issue is exhausting itself," he says. "During the next administration, whomever it may be, the Iranians will either detonate or they will not, so it is time to start thinking not about ways of managing the program, but how do you solve the Iranian conundrum?"
Takeyh says he does not believe a nuclear-armed Iran is inevitable, pointing to the country's economic and political vulnerabilities, along with a robust internal opposition movement that could interrupt Tehran's quest for an atomic bomb.
Still, he says, time is running out.
"In my view, the intellectual challenge here is: How do you get the regime to abide by its international obligations without the use of force? And that is hard to do."
IRAN NUCLEAR TIMELINE