US Secretary of Defense Mark Esper. Photo: VCG

US President Donald Trump has approved sending more US forces to the Gulf which are "defensive in nature" at the requests of Saudi Arabia and the United Arab Emirates (UAE) following the attacks on Saudi oil facilities, said US Secretary of Defense Mark Esper on Friday.

The additional deployment will be "primarily focused on air and missile defense," said the Pentagon chief on Friday evening in a joint press conference with Chairman of the Joint Chiefs of Staff General Joseph Dunford.

Esper's announcement came a week after the drone attacks on oil production facilities in eastern Saudi Arabia, which Washington accused Iran of being responsible for, a claim that has been strongly denied by Tehran.

The additional forces, which were described as a "moderate deployment," would not involve thousands of additional US troops, according to Dunford, who refused to reveal more details.

One of the options that were under discussion within the Trump administration were to send a combination of additional missile defense systems, such as Patriot battery and a Terminal High Altitude Area Defense system, another squadron of fighter jets, and added surveillance capabilities to the Middle East, reported the Wall Street Journal on Thursday.

Blaming Iran for the attacks, Washington rolled out a new round of sanctions on Iran on Friday, targeting its central bank and its national development fund, a move that US Treasury Secretary Steven Mnuchin said would exhaust Tehran's last source of funds.

Also on Friday, Trump told reporters at the White House that ordering military strikes against Iran could be "the easiest thing I could do," adding that "the thing that does show strength would be showing a little bit of restraint."

"I think restraint is a good thing," he added.