The United States announced on Friday it would send military forces to the Gulf following attacks on Saudi oil facilities, hours after Donald Trump ordered new sanctions on Tehran.

Mr 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 rival Saudi Arabia's oil infrastructure, which triggered a spike in global crude prices.

Those attacks, combined with an Iranian attack on an American spy drone in June, represented a "dramatic escalation of Iranian aggression," Secretary of Defense 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.