Donald Trump has approved the deployment of US forces to Saudi Arabia following the attack on two oil facilities in the country.
Troops and military equipment will also be sent to neighbouring United Arab Emirates, a Saudi ally.
The Pentagon described the deployment as “moderate”, adding that forces will be defensive in nature and primarily focused on air and missile defence.
US Marine General Joseph Dunford, chairman of the Joint Chiefs of Staff, said personnel would not be in the thousands but he was not more specific.
The Abqaiq facility and the Khurais oil field were attacked in the early hours of Saturday, causing a reduction of more than half in Saudi Arabia’s daily oil exports – more than 5% of the world’s daily production.
Initially Houthi rebels – backed by Iran – were blamed for the attack. But in recent days, the finger has been pointed directly at Iran.
Defence Secretary Mark Esper said sending troops was a first step and he is not ruling out additional moves in future.
The deployment is a response to a request from the Saudis and UAE to help improve their air and missile defences.
It means that, at least for now, Mr Trump has decided against any military strike on Iran in response to the attacks.
Earlier, he said that restraint “shows far more strength”, as he outlined new sanctions on the Iranian central bank.