"We have 30 to 40,000 American troops stationed across eight or nine facilities in that region," US Secretary of State Marco Rubio told a congressional hearing on Wednesday. "All are within the reach of an array of thousands of Iranian one-way UAVs and Iranian short term ballistic missiles."
"We have to have enough force and power in the region just on a baseline to defend against that possibility that at some point, as a result of something, the Iranian regime decides to strike at our troop presence in the region, the President always reserves the pre-emptive defensive option," he added.
Rubio said the outlook for any transition following the rule of Iran's 86-year-old Supreme Leader remained unclear.
"I don't think anyone can give you a simple answer as to what happens next in Iran if the Supreme Leader and the regime were to fall, other than the hope that there would be some ability to have somebody within their systems that you could work towards a similar transition," he said.
"I would imagine it would be even far more complex than the one we're describing now, because you're talking about a regime that's in place for a very long time."