The United States has announced it will send military reinforcements to the Gulf region following attacks on Saudi oil facilities it blames on Iran, just hours after President Donald Trump ordered new sanctions on Tehran.

Trump said the sanctions were the toughest-ever against another country, but indicated he did not plan a military strike, calling restraint a sign of strength.

The Treasury Department renewed action against Iran’s central bank after US officials said Tehran carried out weekend attacks on Saudi Arabia’s oil infrastructure, which triggered a spike in global crude prices.

Those attacks, combined with an alleged Iranian attack on an American spy drone in June, represented a “dramatic escalation of Iranian aggression”, Secretary of Defence Mark Esper said.

The Pentagon chief 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 defence.”

Joint Chiefs of Staff Joe Dunford categorised the deployment as “moderate,” with the number of troops not expected to reach the thousands. (AFP)