It looks like this is a way of putting pressure on Iran without anything formal coming from the establishment.

An interesting aside is that, to my knowledge, the US has never admitted to having deep penetration special weapons aka bunker busters.

Is this an attempt to convince Iran that they are "on stream" and a possible means of strike? jseal??

What is even more interesting, and rather more subtle, is that the sectarian violence in Iraq stems from Iranian stooges stirring up the shi'ite south. Iran believes that this part of Iraq is really Iranian through ethnic and religious association, wrongly split by the Brits at the end of World War 1. Watch this space.

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