The U.S. Air Force hopes the March 11 demonstration of the new Massive Ordnance Air Blast, a 21,000-pound bomb, will pave the way for its use possibly in Iraq against surface and buried targets. The "Daisy Cutter" bomb, similar to the MOAB but less powerful, was used in Afghanistan against the Taliban and during the Persian Gulf War to clear minefields and in psychological operations against Iraqi troops. Here is a comparison of the two bombs: MOAB - Massive Ordnance Air Blast aka "the mother of all bombs"

Primary function: Originally designed to target large formations of troops and equipment or hardened above-ground bunkers. Also, U.S. military officials say the MOAB was conceived as a weapon employed for "psychological operations."
Weight: 21,000 lbs.
Explosive power: 18,000 lbs. of tritonal explosives
Deployed: C-130 cargo aircraft

 

"Daisy Cutter"
BLU-82 aka "Daisy Cutter"

Primary function: Originally designed to clear helicopter landing zones and artillery emplacements in Vietnam. During Operation Desert Storm, the U.S. military says the initial drops were intended to test the ability of the bomb to clear minefields, but the "daisy cutters" were used later for psychological purposes.
Weight: 15,000 lbs.
Explosive power: 12,600 lbs. of the less powerful GSX explosives (ammonium nitrate, aluminum powder and polystyrene)
Length: 141.6 in.
Diameter: 54 in.
First used: Vietnam on March 23, 1970. It was used for the duration of the war for tactical airlift missions called "Commando Vault."
Deployed: C-130 cargo aircraft
Source: U.S. Air Force; Federation of American Scientists

 

ISOCT theorizes that this announcement may well be a thinly veiled threat directed at North Korea. If North Korea continues to defy the nuclear weapons non-proliferation treaty by continuing it's nuclear weapons program, the U.S. could use the MOAB creating little collateral damage. This would either fuel or cause North Korea to cease and desist.