Part of why we went into Iraq was to establish a US base in the Middle East. Presumably we have nuclear subs over there, one or two? And why were we talking loudly two weeks ago about the MOAB, 300,000 lbs., that we'd just built. This would make sawdust of concrete/steel reinforced bunkers of any depth. Was this bit of Pentagon news information aimed at Iran? If so, we got our answer.
The new moab won't be flight tested until 2006, IIRC. The first contract is due to be awarded in 6 days.
We really don't have any deep weapons in inventory. We could machine gun the target to expose enough surface to get a standard moab in there, but I'm not sure it's heavy enough.
My guess is that the reason President Bush wants to develop the new tactical nukes is to restore parity. We have no way to penetrate the underground cities and bunkers that have been completed by those who intend to win a nuclear war.