Prime Minister Binyamin Netanyahu told CNN from London on Thursday that Iranian "supreme leader" Ayatollah Khamenei is the greatest threat to world peace.

Netanyahu said that as the final and supreme authority in the Islamic Republic, Khamenei was more of a problem than President Mahmoud Ahmadinijad.

"He runs the country and he is infused with fanaticism," Netanyahu said of Khamenei, in reference to Iran's nuclear program.

Netanyahu told CNN that Iran's obtaining nuclear weapons would change history. 

"The future of the world - the future of the Middle East - is certainly at stake," Netanyahu said.

Only sanctions backed by a creditable military threat, Netanyahu maintained, could prevent Iran's nuclear ambitions from coming to fruition.

"Those sanctions might work if the international community makes it clear that there is a credible military option if sanctions don't work," Netanyahu said.

Netanyahu was equally circumspect about the "Spring Revolution" that has swept through the Middle East.

"Something very big is happening here, a convulsion," Netanyahu said. "We would like to see the triumph of democracy... that's something that will guarantee the peace."

But he also warned Islamists might hijack democratic revolutionary movements.

"The biggest threat is the possibility that a militant Islamic regime will acquire nuclear weapons -- or that nuclear weapons could acquire a militant Islamic regime."