I’d take it one step further. There are other sources that indicate that Imanutjob and the radical fringe is in an increasing bitter struggle with the old guard religious leaders. He wants the Madhi to arrive, they just want to stay in power. The Madhi arrives through war, conflict will either kill the old guard, or cause enough turmoil that the internal factions wanting a more democratic rule will be able to rise up and overthrow them. Thus, to prevent further set backs, Imanutjob will have to maneuver two elements - the old guard imans as well as tweaking the US/Brit forces, so that he cannot suffer another set back and can move forward with his vision of conflict.
It seems his best bet, then, is stoking conflict between the two so that he can sit back and wait by the well for the 12th imam while everyone else dukes it out. It’s a safe bet that almost any action by the US will turn some of the anti-government elements within the country against us, and throw them on the side of Khameini, Ahmadinejad, or both. All he has to do is get us to unwittingly hit a sensitive and sympathetic target, and a number of people will fall off the fence on their side.