Signal to Iran? Pentagon bulks up its 'bunker buster' bomb. VIDEO.

Named 'Massive Ordinance Penetrator.

The MOP is approximately 20.5 feet long, with a 31.5-inch diameter and a total weight of slightly less than 30,000 pounds. The weapon will carry over 5,300 pounds of explosive material and will deliver more than 10 times the explosive power of its predecessor, the BLU-109. It is designed to penetrate up to 200 feet underground before exploding. (U.S. Air Force photo)

WASHINGTON, May 3 (UPI) -- The Pentagon has beefed up its biggest "bunker buster" bomb so it can destroy Iran's most heavily armed and protected nuclear site, U.S. officials said.

The administration believes the enhanced Massive Ordnance Penetrator, the Pentagon's largest conventional bomb, will decrease the chances Israel will launch a unilateral bombing campaign against Iran, at least for this year and maybe next year too, the officials told The Wall Street Journal .

This would buy more time for the Obama administration to pursue diplomacy after Iran holds elections in June.

It could also give the West more influence in diplomatic efforts to persuade Iran to rein in its nuclear program.

Israel and Iran had no immediate comment. Jerusalem maintains it reserves the right to attack Iran. Iran maintains its nuclear program is solely peaceful.

The upgraded MOP, a precision-guided, 30,000-pound behemoth, is designed to destroy Iran's deep-underground Fordo uranium-enrichment plant south of Tehran, near the holy city of Qom.

Fordo was previously seen as largely immune to U.S. or Israeli military strikes, officials said.

But the bulked-up MOP features adjusted fuses to greatly enhance its ability to penetrate into soil, rock and concrete, the Journal said.

The "smart weapon" also has improved guidance systems to improve its ability to precisely hit the plant and minimize collateral damage, the newspaper said.

And it has high-tech equipment to help it elude Iranian air defenses.

The upgraded MOP hasn't been dropped from a plane yet, the Journal said.

"Hopefully we never have to use it," a senior U.S. official told the newspaper. "But if we had to, it would work."