Israel has launched a covert war against Iran as an alternative to direct military strikes against Tehran's nuclear programme, US intelligence sources have revealed.
It is using hitmen, sabotage, front companies and double agents to disrupt the regime's illicit weapons project, the experts say.
The most dramatic element of the "decapitation" programme is the planned assassination of top figures involved in Iran's atomic operations.
Despite fears in Israel and the US that Iran is approaching the point of no return in its ability to build atom bomb, Israeli officials are aware of the change in mood in Washington since President Barack Obama took office.
They privately acknowledge the new US administration is unlikely to sanction an air attack on Iran's nuclear installations and Mr Obama's offer to extend a hand of peace to Tehran puts any direct military action beyond reach for now.
The aim is to slow down or interrupt Iran's research programme, without the gamble of a direct confrontation that could lead to a wider war.
A former CIA officer on Iran told The Daily Telegraph: "Disruption is designed to slow progress on the programme, done in such a way that they don't realise what's happening. You are never going to stop it.
"The goal is delay, delay, delay until you can come up with some other solution or approach. We certainly don't want the current Iranian government to have those weapons. It's a good policy, short of taking them out militarily, which probably carries unacceptable risks."
Reva Bhalla, a senior analyst with Stratfor, the US private intelligence company with strong government security connections, said the strategy was to take out key people.
"With co-operation from the United States, Israeli covert operations have focused both on eliminating key human assets involved in the nuclear programme and in sabotaging the Iranian nuclear supply chain," she said.
"As US-Israeli relations are bound to come under strain over the Obama administration's outreach to Iran, and as the political atmosphere grows in complexity, an intensification of Israeli covert activity against Iran is likely to result."
Mossad was rumoured to be behind the death of Ardeshire Hassanpour, a top nuclear scientist at Iran's Isfahan uranium plant, who died in mysterious circumstances from reported "gas poisoning" in 2007.
Other recent deaths of important figures in the procurement and enrichment process in Iran and Europe have been the result of Israeli "hits", intended to deprive Tehran of key technical skills at the head of the programme, according to Western intelligence analysts.
"Israel has shown no hesitation in assassinating weapons scientists for hostile regimes in the past," said a European intelligence official, speaking on condition of anonymity. They did it with Iraq and they will do it with Iran when they can."