The Pentagon is speeding up delivery of a colossal bomb designed to destroy hidden weapons bunkers buried underground and shielded by 10,000 pounds of reinforced concrete.

Call it Plan B for dealing with Iran, which recently revealed a long-suspected nuclear site deep inside a mountain near the holy city of Qom.

The 15-ton behemoth — called the "massive ordnance penetrator," or MOP — will be the largest non-nuclear bomb in the U.S. arsenal and will carry 5,300 pounds of explosives. The bomb is about 10 times more powerful than the weapon it is designed to replace.