The Biden administration’s monthslong effort to avert a full-blown war between Israel and Iran is now being put to the most difficult test yet after Tehran on Tuesday launched a barrage of ballistic missiles at Israel.

The administration has worked around the clock for the past year trying to avoid a direct clash between its ally Israel and Iran. But now, administration officials are facing a potential worst-case scenario, as the latest attack by Iran will inevitably trigger a retaliation…