Looks like The White House is just winging it, and there's no plan whatsoever:

A recent internal assessment from the Defense Intelligence Agency that was circulating inside the Pentagon in recent weeks determined that Iran could potentially keep the passage shut for anywhere from one to six months, four sources familiar with the document told CNN. But White House and Pentagon officials insisted that the assessment — particularly the longer end timeframe, which some consider a worst-case scenario — was not being seriously considered.