The US Air Force has a new 30,000-pound bomb in its arsenal designed to penetrate targets buried deep underground, a spokesman said Tuesday.

The Air Force started taking delivery of the giant bomb, the "Massive Ordnance Penetrator," in September, said Lieutenant Colonel Jack Miller.

Under an August 2 contract worth $32 million, the aerospace firm Boeing is due to produce eight of the giant MOP bombs to fulfil the Air Force's "operational needs," according to Miller.

The Air Force could not say how many of the conventional bombs have been delivered so far, but the MOP is seen as a weapon made for going after underground bunkers and tunnels in North Korea or Iran.

The MOP bomb, with more than 5,000 pounds (or nearly 2.5 tons) of explosives, is supposed to fit on a B-2 stealth bomber to strike at underground sites hiding weapons of mass destruction.

About 20 feet (six meters) long, the GPS-guided bomb "will defeat our adversaries WMD before they leave the ground," according to an official description posted on the website of the Defense Threat Reduction Agency and US Strategic Command.

The United States, which suspects Iran and North Korea have built nuclear facilities deep underground to thwart any possible air raids, has been developing the MOP bomb since about 2007.

The weapon, made to penetrate up to 200 feet of reinforced concrete before exploding, is ten times more powerful than its predecessor, the BLU-109.

The new MOP is also twice as heavy as the "daisy cutter" bomb employed in Vietnam and in Tora Bora at the outset of the war in Afghanistan.

The "daisy cutter" has since been retired and replaced with the MOAB, the Massive Ordnance Air Blast bomb or "the Mother of All Bombs," which weighs less than the MOP bomb but contains more explosive power.