US 'bunker-buster' not powerful enough against Iran

WASHINGTON (AFP) - The US military has concluded that its largest conventional bomb is not capable of destroying Iran's most heavily fortified underground facilities suspected to be used for building nuclear weapons, The Wall Street Journal reported late on Friday.

But citing unnamed US officials, the newspaper said the military was stepping up efforts to make it more powerful.

The 12.3-tonnes 'bunker-buster' bomb, known as the Massive Ordnance Penetrator, was specifically designed to take out the hardened fortifications built by Iran and North Korea, the report said.

But initial tests indicated that the bomb, as currently configured, would not be capable of destroying some of Iran's facilities, either because of their depth or because Teheran has added new fortifications to protect them, the paper noted.