If Congress agrees to shift enough funds to the program, Northrop Grumman Corp (NOC.N)'s radar-evading B-2 bomber "would be capable of carrying the bomb by July 2010," said Andy Bourland, an Air Force spokesman.

"The Air Force and Department of Defense are looking at the possibility of accelerating the program," he said. "There have been discussions with the four congressional committees with oversight responsibilities. No final decision has been made."

The precision-guided weapon, built by Boeing Co (BA.N), could become the biggest conventional bomb the United States has ever used.

Carrying more than 5,300 pounds of explosives. it would deliver more than 10 times the explosive power of its predecessor, the 2,000-pound BLU-109, according to the Pentagon's Defense Threat Reduction Agency, which has funded and managed the seed program.

Chicago-based Boeing, the Pentagon's No. 2 supplier by sales, could be put on contract within 72 hours to build the first MOP production models if Congress signs off, Bourland said.

The threat reduction agency is working with the Air Force to transition the program from "technology demonstration" to acquisition, said Betsy Freeman, an agency spokeswoman.

Both the U.S. Pacific Command, which takes the lead in U.S. military planning for North Korea, and the Central Command, which prepares for contingencies with Iran, appeared to be backing the acceleration request, said Kenneth Katzman, an expert on Iran at the Congressional Research Service, the research arm of Congress.

"It's very possible that the Pentagon wants to send a signal to various countries, particularly Iran and North Korea, that the United States is developing a viable military option against their nuclear programs," Katzman said.

But he cautioned against concluding there was any specific mission in mind at this time.

BIGGEST BOMB

The MOP would be about one-third heavier than the 21,000-pound (9.5 million kg) GBU-43/B Massive Ordnance Air Blast bomb -- dubbed the "mother of all bombs" -- that was dropped twice in tests at a Florida range in 2003.

The 20-foot-long (6-metre) MOP is built to be dropped from either the B-52 or the B-2 "stealth" bomber. It is designed to penetrate up to 200 feet (61 metres) underground before exploding, according to the U.S. Air Force.

The suspected nuclear facilities of Iran and North Korea are believed to be largely buried underground to escape detection and boost their chances of surviving attack.

During a visit to Jerusalem last week, U.S. Defense Secretary Robert Gates sought to reassure Israel that a drive by President Barack Obama to talk Iran into giving up its nuclear work was not "open-ended."

Iran says its uranium enrichment -- a process with bomb-making potential -- is for energy only and has rejected U.S.-led demands to curb the program.

For its part, North Korea responded to new United Nations sanctions, imposed after it detonated a second nuclear device, by vowing in June to press the production of nuclear weapons and act against international efforts to isolate it.