I think that one of the main things to take into consideration when deciding on a delivery vehicle for the warhead would be that the object would need to be taken care of a lot farther away from earth than Hollywierd would have you believe. A hit weeks/months before the object were to collide with the Earth would be needed to deflect it sufficiently. What do we have READY to make this long of a journey?

Due to the fact that the nuclear detonation would be in a near vacuum, I believe that the device would have to be detonated in contact with the object to have sufficient effect too. Do we have a guidance system READY that would provide the terminal guidance for this? The ABM guidance system?