US Defence Secretary Mark Esper said the move would be "defensive in nature" but officials have not yet decided how many troops will be sent.
Soldiers and military equipment will also be sent to Saudi ally the neighbouring United Arab Emirates.
Yemen's Iran-backed Houthi rebels have claimed responsibility for last week’s attack on the Saudi oil industry which saw strikes on the country’s Abqaiq facility and the Khurais oil field.
But the US and Saudi Arabia have both blamed Iran. Iran has denied involvement.
The announcement follows the US president’s announcement of new sanctions against Iran, while signalling his desire to avoid military conflict.
"I think the strong person approach, and the thing that does show strength, would be showing a little bit of restraint," he told reporters in the Oval Office on Friday during a meeting with Australian Prime Minister Scott Morrison.
"Because the easiest thing I could do, 'Okay, go ahead. Knock out 15 different major things in Iran'. But I'm not looking to do that if I can," he added.
The deployment of troops was described by Mr Esper as a first step towards beefing up security in the region.
The Pentagon would not rule out additional moves in the future, he added.
General Joseph Dunford, chairman of the Joint Chiefs of Staff, said more details about the move will be determined in the coming days, but it would not involve thousands of US troops.
Mr Dunford told reporters the extra equipment and troops would give the Saudis a better means of defence against unconventional aerial attacks.
"No single system is going to be able to defend against a threat like that," he said. "But a layered system of defensive capabilities would mitigate the risk of swarms of drones or other attacks that may come from Iran."
Smoke billows from refinery after drone attack in Saudi Arabia
The US has not provided any hard evidence that Iran was responsible for the attacks, while insisting the investigation continues, but Mr Esper said the drones and cruise missiles used in the attack were produced by Iran.
On Wednesday, the kingdom's defence ministry revealed what it claims were the remains of drones and cruise missiles proving Iranian involvement.
The country is still "working to know exactly the launch point", a spokesman said.
Mr Esper said the US had so far shown "great restraint" in response to last week’s attacks.
He said: "The attack on September 14 against Saudi Arabian oil facilities represents a dramatic escalation of Iranian aggression.”
In deciding against an immediate US strike, Mr Trump for the second time in recent months pulled back from a major military action against Iran that many Pentagon and other advisers fear could trigger a new Middle East war.
In June, after Iran shot down an American surveillance drone, Mr Trump initially endorsed a retaliatory military strike then abruptly called it off because he said it would have killed dozens of Iranians.
On Friday, he left the door open for a later military response, saying people thought he would attack Iran "within two seconds" but he has "plenty of time".