The United States said it will send military reinforcements to the Gulf region following attacks on two Saudi oil facilities last week, which the US blamed on Iran.
Houthi rebels in Yemen said they carried out the attack but the US and Saudi Arabia said they believe Tehran - which supports the rebels in their fight against a Saudi-led coalition - was behind the attack.
The attack halved Saudi Arabia's oil production and triggered a spike in global crude oil prices.
The acting US Secretary of Defence, Mark Esper, announced that the United States would send military reinforcements to the Gulf region at the request of Saudi Arabia and the United Arab Emirates.
"In response to the kingdom's request, the president has approved the deployment of US forces, which will be defensive in nature, and primarily focused on air and missile defense," said Mr Esper.
However Joint Chiefs of Staff Joe Dunford categorised the deployment as "moderate", with the number of troops not expected to reach the thousands.
Earlier, President Trump attacked critics who thought he would trigger war.
"The easiest thing I could do (is) knock out 15 different major things in Iran," said Mr Trump..
"But I think the strong-person approach and the thing that does show strength would be showing a little bit of restraint," said the US president.