But the veteran politician also publicly acknowledged the extent of debate and disagreement within Israel's political and military echelons over the merits of a military strike.

He told an international conference in Herzliya, Israel, on Thursday: "The world today has no doubt that the Iranian military nuclear program is slowly but surely reaching the final stages and will enter the immunity stage, from which point the Iranian regime will be able to complete the program without any effective intervention and at its convenience."

At that point it would be impractical to attack, he said.

"Dealing with a nuclearized Iran will be far more complex, far more dangerous and far more costly in blood and money than stopping it today. In other words, those who say 'later' may find that later is too late," said Barak.