The US has approved plans for a series of strikes on Iranian targets in Syria and Iraq.
The strikes will take place over a number of days, officials said, and weather conditions will likely dictate when they are launched.
It comes after a drone attack killed three US soldiers in Jordan, close to the Syrian border, on Sunday.
The US blamed an Iranian-backed militia group, the Islamic Resistance in Iraq, for that attack. The US intelligence believes that the drone used to attack the facility was manufactured by Iran – and is similar to the drones Iran has been sending to Russia for its invasion of Ukraine.
Iran, meanwhile, has denied any role in the attack which injured 41 other US troops at the military base, known as Tower 22.