Donald Trump is dispatching additional forces to Saudi Arabia following the attack on oil facilities that the US has blamed on Iran.

A week after Saudi oil facilities at Khurai and Abqaiq were damaged – in an operation that Houthi rebels in Yemen claimed responsibility for and which temporarily halved the kingdom’s oil production – the Pentagon announced it was be deploying a “moderate” number of troops primarily “defensive in nature”.

US marine general Joseph Dunford, chair of the joint chiefs of staff, and secretary of defence Mark Esper told reporters in Washington the deployment would not reach thousands of troops, but they declined to be more specific.

There was no mention of possible strikes against Iran, something Mr Trump has raised the prospect of, but also said he wanted to avoid.

Mr Esper, who said “all indications” were that Iran was responsible for the attacks despite Tehran’s denial, said the move was a first measure.

Attack on major oil facilities in Saudi Arabia: In pictures Show all 10 1 /10 Attack on major oil facilities in Saudi Arabia: In pictures Attack on major oil facilities in Saudi Arabia: In pictures Smoke billows from multiple fires at the Aramco oil processing facility in Abqaiq, Saudi Arabia on 14 September Reuters Attack on major oil facilities in Saudi Arabia: In pictures Thick black smoke billows from a fire following drone strikes on major oil facilities in Abqaiq, Saudi Arabia Planet Labs Inc/Reuters Attack on major oil facilities in Saudi Arabia: In pictures The Aramco oil processing facility in Abqaiq, Saudi Arabia prior to the drone strikes on 14 September AP Attack on major oil facilities in Saudi Arabia: In pictures Damage is seen to the Aramco oil processing facility in Abqaiq, Saudi Arabia following drone strikes on 14 September, the previous day (Image 1 of 2) AP Attack on major oil facilities in Saudi Arabia: In pictures Damage is seen to the Aramco oil field in Abqaiq, Saudi Arabia following drone strikes on 14 September, the previous day (Image 2 of 2) AP Attack on major oil facilities in Saudi Arabia: In pictures Damage is seen to the Aramco oil field in Khurais, Saudi Arabia following drone strikes on 14 September, the previous day (Image 1 of 2) AP Attack on major oil facilities in Saudi Arabia: In pictures Damage is seen to the Aramco oil field in Khurais, Saudi Arabia following drone strikes on 14 September, the previous day (Image 2 of 2) AP Attack on major oil facilities in Saudi Arabia: In pictures Smoke billows from multiple fires following drone strikes on major oil facilities in Abqaiq, Saudi Arabia AFP/Getty Attack on major oil facilities in Saudi Arabia: In pictures Smoke rises from a fire following a drone strike at the Aramco facility in Abqaiq, Saudi Arabia on 14 September Reuters Attack on major oil facilities in Saudi Arabia: In pictures Smoke is seen following a fire at the Aramco oil processing facility in Abqaiq, Saudi Arabia on 14 September Reuters

Anywhere up to 5,000 troops are already in Saudi Arabi, and the Pentagon announced as recently as July it was deploying a further 500 soldiers as tensions with Iran mounted.

The news followed an announcement by Mr Trump that the US was imposing new sanctions on Iran.

“I think the sanctions work,” Mr Trump said in the Oval Office, where he was meeting Australian prime minister Scott Morrison.

Drone attacks spark huge fire at Saudi Aramco, the world's biggest oil processing facility

“We have just sanctioned the Iranian national bank. These are the highest sanctions ever imposed on a country.”

He added: “The easiest thing I could do is knock out 15 different major things in Iran. I could do it right here in front of you. And that would be it. And then you would have a nice, big story to report.

“‘But I think the strong-person approach and the thing that does show strength would be showing a little bit of restraint.”

There had been anticipation Mr Trump might meet Iranian president, Hassan Rouhani, next week on the sidelines of the UN summit in New York.

That now seems all but certain not to happen.