In an announcement that could signal military engagement with Iran, President Bush said he had authorized "whatever actions are necessary to counter Iranian agents deemed a threat to American troops or the public at large," which of course can mean just about anything.
Bush did say that the US does not intend to cross the Iraqi-Iran border in pursuit of these agents, but also did not completely rule it out. But as we know from history with this administration that little bit of wiggle room can make all the difference.
Justifying this new policy is reported "intelligence" that Iran is supplying Iraqi insurgents with material and training on improvised explosive devices (IEDs) that are increasingly killing American troops. Nevermind the fact that hundreds of adandoned ammo dumps with literally tons of munitions were left unguarded in the months after the US invasion and that early reports on these IEDs cited those dumps as the sources for these devices. If Bush is citing intelligence in an argument for military engagement, you can bet it's a "slam dunk."