"If Israel takes such a stupid step and attacks, the answer of Iran and its Revolutionary Guard will be rapid, firm and destructive and it will be given in a few seconds," he said.
He also said the country was pressing ahead with plans to expand its program to enrich uranium, which the West and Israel say Iran is using to make nuclear warheads despite Tehran's denials.
In an interview appearing Sunday in Newsweek and the Washington Post, Olmert compared Iranian president Mahmoud Ahmadinejad to Adolf Hitler, calling Ahmadinejad "a man who is ready to commit crimes against humanity" and noting "he has to be stopped."