Potential use of tactical nuclear weapons by the United States in Iran would be a catastrophic development, Russian state news agency TASS quoted Kremlin spokesman Dmitry Peskov as saying on Friday.

Iran's progress toward having a nuclear weapon is central to the current conflict between Israel and Iran. Before launching recent attacks against Iran's nuclear sites, Israel said it had evidence Tehran was on the brink of building a nuclear weapon.

With Donald Trump mulling whether to send in American bunker-busting bombs to deal a crushing blow to Iran’s nuclear facilities, doubts remain about just how close Iran is to creating a nuclear bomb.