The former chief of Israel's Mossad spy agency has cautioned against an attack on Iran's nuclear sites and put his trust firmly in US President Barack Obama to intervene if and when necessary.

In excerpts of an interview with CBS's "60 Minutes" program to be aired in full on Sunday, Meir Dagan said he believes the Iranian regime is a "very rational one," including firebrand President Mahmoud Ahmadinejad.

"An attack on Iran before you are exploring all other approaches is not the right way," Dagan said.

"And (President Obama) said openly that the military option is on the table and he is not going to let Iran become a nuclear state, and from my experience, I usually trust the president of the US."

The Obama administration maintains that tough sanctions on Iran and diplomatic efforts need to be given more time before any resort to bombing raids.