New top secret intelligence documents have revealed Iran is working on a key final component of a nuclear bomb.
The papers document Iran's most sensitive military nuclear project, the London Sunday Times reported.
It outlines a four-year plan to test the trigger device on a bomb called a "neutron initiator." According to experts, the device has no possible civilian or military use other than being used in a nuclear weapon.
The plan dates the papers to early 2007. That's a full four years after experts thought Iran had suspended its weapons program.
Mark Fitzpatrick of the International Institute for Strategic Studies told the Times: "The most shattering conclusion is that, if this was an effort that began in 2007, it could be a casus belli."
"If Iran is working on weapons, it means there is no diplomatic solution. Is this the smoking gun? That's the question people should be asking. It looks like the smoking gun. This is smoking uranium."