When asked about what would happen in the aftermath of an Israeli attack Dagan said that: "It will be followed by a war with Iran. It is the kind of thing where we know how it starts, but not how it will end."

The Iranians have the capability to fire rockets at Israel for a period of months, and Hizbollah could fire tens of thousands of grad rockets and hundreds of long-range missiles, he said.

At the same time, Tehran can activate Hamas, and there is also a danger that Syria will join the war, Dagan added.

Dagan said that Iran has a clandestine nuclear infrastructure which functions alongside its legitimate, civil infrastructure. It is the legitimate infrastructure, he said, that is under international supervision by the International Atomic Energy Agency (IAEA). Any strike on this legitimate infrastructure would be "patently illegal under international law," according to Dagan.

Dagan emphasized that attacking Iran would be different than Israel's successful air strike on Iraq's nuclear reactor in 1981. Iran has scattered its nuclear facilities in different places around the country, he said, which would make it difficult for Israel to launch an effective attack.