June 10, 2013:
Israeli media are reporting recent U.S. tests of its 14 ton deep penetrator bomb (the MOP or Massive Ordnance Penetrator, a.k.a the GBU-57) against an accurate replica of the main Iranian nuclear weapons development facility at Fordo. Apparently the results of this test were distributed to American allies with the intention of sending a message to Iran. There is no confirmation of such a test.
It was only two years ago that the first eight GBU-57s were ordered and about twenty have been obtained so far. Earlier this year the U.S. Air Force announced unspecified improvements to the GBU-57. Seven of the first eight production model bombs were used for tests, which resulted in a classified list of tweaks to the existing design and these upgrades have been added regularly over the last year. All this apparently paid off in the recent test against the Fordo replica.
The GBU-57 contains 2.4 tons of explosives and costs $3.5 million each. In the last few years several B-2 bombers have been equipped to carry these weapons (two bombs per B-2). This was apparently meant to send a message to Iran and North Korea. There were no known targets for such a weapon anywhere else, but there are plenty of such targets in Iran and North Korea. Moreover, even if there were deep bunkers in Somalia or Afghanistan you don't need a stealth bomber to deliver an MOP. The enemy in those countries have no way of detecting a high flying B-52, much less a stealthy B-2. But Iran and North Korea do have radars, and a B-2 could slip past those radars and take out the air defense system command bunkers, or any other targets buried deep.
The 6.2 meter (20.5 foot) long MOP has a thick steel cap, which was originally designed to penetrate up to 7.9-61 meters (26-200 feet) of concrete (depending on degree of hardness) or up to 61 meters of rocky earth before exploding. This was the original spec, which is now supposed to be improved. A new Iranian nuclear facility (Fordo) is supposed to be buried beneath 90 meters of earth and rock.
The U.S. has not (officially) sold any GBU-57s to Israel, so any use of this bomb would have to be by American aircraft.