The Pentagon says the US will deploy additional troops and military equipment to Saudi Arabia and the United Arab Emirates to beef up security.
President Donald Trump has, at least for now, decided against any immediate military strike on Iran in response to the attack on the Saudi oil industry.
Defence Secretary Mark Esper says this is a first step, and he is not ruling out additional moves later.
He says it is a response to requests from the Saudis and the UAE to help improve their air and missile defences.
Mr Esper and Gen Joseph Dunford, chairman of the Joint Chiefs of Staff, say details of the deployments will be determined over the coming days.
Mr Trump said he believes showing restraint “shows far more strength” and he wants to avoid an all-out war.