PITTSBURGH (AFP) - Bombshell claims about Irans secret uranium plant reveal a tale of years of clandestine espionage by Western spies peering into the hidden heart of Tehrans nuclear program. Senior officials from the US, France and Britain offered a tantalising glimpse Friday into a joint intelligence operation tracking what the West says is Irans drive to build a nuclear bomb. Our intelligence services working in very close cooperation with our allies for the past several years have been looking for such a facility, said one US official. And not surprisingly we found one. A French official said that construction at Qom started four years ago - before fiery Mahmoud Ahmadinejad was elected Iranian president. Another source said the work on the secret plant started in earnest in 2006. So why would the western powers wait so long to reveal it? One US official said it would have been a terrible mistake to go public before intelligence agencies had time to build an undeniable case. Fridays revelations also hinted at high stakes decisions behind closed doors in Washington, Paris and London, as the allies worked out how best to use their explosive information.