Shapiro served as Deputy Assistant Secretary of Defense for the Middle East until January—charged with, among other things, considering scenarios in which tensions between Israel and Iran escalated into all-out war and preparing U.

Israel and Iran traded missile fire for a fifth straight day Tuesday, as U.S. President Donald Trump warned Tehran residents to "immediately evacuate" and left a G7 summit early.

Israel has struck major nuclear and military sites and killed leading commanders and nuclear scientists in Iran, which has responded with its own volley of drones and missiles on Israel.

Iranian officials have warned that U.S. participation in an attack on its facilities will imperil any chance of the nuclear disarmament deal the president insists he is still interested in pursuing.

Israel and Iran have begun a new round of attacks, as the conflict between the two heavily armed rivals enters its fourth day.

President Donald Trump warned that "it's possible" that the United States "could get involved" in the ongoing Israel-Iran conflict if it continues to escalate during an exclusive interview with ABC News' Rachel Scott on Sunday (June 15).

"American Forces are maintaining their defensive posture & that has not changed," the chief Pentagon spokesperson said.

The president had opposed Israeli action against Iran but came to believe that Israel had reason to act and that the U.S. would have to lend some support.