Boris Johnson has blamed Iran for the attacks on Saudi Arabian oil facilities, before a meeting with President Hassan Rouhani.

The Prime Minister said on Sunday that the UK could attribute blame with a “very high degree of probability” to the Islamic republic as he declined to rule out military intervention.

The PM told reporters on board the RAF Voyager to New York that he would meet with the Iranian leader at the United Nations General Assembly.

He said he would also raise the case of Nazanin Zaghari-Ratcliffe during discussions on Tuesday afternoon.

The US and Saudi Arabia have already accused Iran of being behind the September 14 raids on the world’s largest oil processor and an oil field, causing a spike in prices. Tehran has issued denials.

But Mr Johnson gave the first attribution of blame from the UK before landing in the US in the early hours of Monday UK-time.

“I can tell you that the UK is attributing responsibility with a very high degree of probability to Iran for the Aramco attacks,” he said.

“We think it very likely indeed that Iran was indeed responsible for using both UAVs (unmanned aerial vehicles), both drones and cruise missiles.

“Clearly the difficulty is, how do we organise a global response? What is the way forward?

“And we will be working with our American friends and our European friends to construct a response that tries to deescalate tensions in the Gulf region.”

Nazanin Zaghari-Ratcliffe detained in Iran
British mother Nazanin Zaghari-Ratcliffe with her husband Richard Ratcliffe and their daughter Gabriella (Supplied/PA)

The PM said he would “follow very closely” American proposals to do more to defend Saudi Arabia, with Tehran’s ire being further provoked by the US-led coalition patrolling the region’s waterways.

“And clearly if we are asked either by the Saudis or the Americans to have a role then we would consider in what way we could be useful,” he said.

Asked if military action was possible, he replied: “We will consider in what way we could be useful if asked and depending on what the exact plan is.”

Sanctions also remained on the table.

The PM was speaking ahead of a joint meeting with French President Emmanuel Macron and German Chancellor Angela Merkle at the UN.

It was billed as an E3 meeting to discuss the Aramco attacks, but Brexit talks are also expected to be dominant.

Mr Johnson is also set to meet US President Donald Trump. They have already discussed the need for a “united diplomatic response” to the attacks.

The PM said he would bring up the case of Ms Zaghari-Ratcliffe and other dual nationals being held in Tehran when he meets Mr Rouhani.

Mr Johnson has come under intense criticism over his handling of the British-Iranian mother’s case as foreign secretary.

She is midway through a five-year jail sentence for spying charges, which she has always denied.

“In the course of my conversation with President Rouhani, I will not only be discussing Iran’s actions in the region, but also the need to release not just Nazanin but others who in our view are being illegally and unfairly held in Tehran,” he said.

The UK was dismissing claims by Yemen’s Houthi movement that it was behind the Aramco attacks.

A Whitehall source said: “The Houthi’s claim of responsibility is implausible.

“Imagery from the site of the attack shows the remnants of Iranian-made land attack cruise missiles and the scale, sophistication and range of the attack is inconsistent with the Houthi’s capability.”