Israel's attack came while Tehran was negotiating with the United States and was not making any drastic military moves, the supreme leader said.
"God Almighty will surely make it so that the Iranian people will truly win," Khamenei said in a statement.
Israel made a big mistake by attacking Iran, the supreme leader said, adding that Tehran has a plan for "further retaliation."
Additionally, he said that the damage to the US from its military intervention in the conflict with Iran will be much greater than the damage Iran will suffer.