Israel's intelligence service Mossad agrees with US assessments there is no hard evidence that Iran has decided to build a nuclear bomb, even though Israeli leaders have talked about Tehran's plans to acquire nuclear weapons, The New York Times reported.

"Their people ask very hard questions, but Mossad does not disagree with the US on the weapons program," the newspaper quoted an unnamed former senior US intelligence official as saying.

"There is not a lot of dispute between the US and Israeli intelligence communities on the facts," the former official said.

The Times reported last month that the latest assessments by US spy agencies are broadly consistent with a 2007 intelligence finding that concluded that Iran had abandoned its nuclear weapons program.

According to Saturday's report, US spy agencies have spent years trying to track Iranian efforts to enrich uranium and develop missile technology, and they are watching for any move toward weaponization.

While the National Security Agency eavesdrops on telephone conversations of Iranian officials and conducts other forms of electronic surveillance, the National Geospatial-Intelligence Agency analyzes radar imagery and digital images of nuclear sites, the paper noted.

Outside analysts believe high-tech drones prowl over secret Iranian installations, The Times pointed out.

Meanwhile, clandestine ground sensors, which can detect electromagnetic signals or radioactive emissions that could be linked to covert nuclear activity, are placed near suspect Iranian facilities, according to the report.

The United States also relies heavily on information gathered by inspectors with the International Atomic Energy Agency who visit some of Iran's nuclear-related facilities, The Times said.