The US is on high alert and actively preparing for a “significant” attack that could come as soon as within the next week by Iran targeting Israeli or American assets in the region in response to Monday’s Israeli strike in Damascus that killed top Iranian commanders, a senior administration official tells CNN.

Senior US officials currently believe that an attack by Iran is “inevitable” – a view shared by their Israeli counterparts, that official said. The two governments are furiously working to get in position ahead of what is to come, as they anticipate that Iran’s attack could unfold in a number of different ways – and that both US and Israeli assets and personnel are at risk of being targeted.

A forthcoming Iranian attack was a major topic of discussion on President Joe Biden’s phone call with Israeli Prime Minister Benjamin Netanyahu on Thursday.

As of Friday, the two governments did not know when or how Iran planned to strike back, the official said.