Israel is bracing for a possible attack from Iran, either directly or via its proxies, with drones and missiles on government targets within days, according to people familiar with western intelligence assessments, a move that has the potential to trigger an all-out regional war.

An assault is expected to come as soon as the next 48 hours, said the people, who asked not to be identified as they aren’t authorized to discuss the matter publicly. One scenario is an attack on Israel from Iranian soil, which would be unprecedented, they said.

The move still hasn’t been approved by Tehran’s highest-ranking officials, the people said. The US is preparing defenses and has moved additional military assets to the region, while intensifying diplomatic efforts to rein in hostilities, they said.

A missile and drone barrage would represent a retaliation by Iran for a deadly attack on its diplomatic compound in Syria last week, which the Islamic Republic blames on Israel. Supreme Leader Ayatollah Ali Khamenei has repeatedly said Israel will be “punished” for the assault, though stopped short of saying what form such a counter move would take.