Britain has joined the U.S. in blaming Iran for recent attacks on oil facilities in Saudi Arabia, U.K. Prime Minister Boris Johnson said Sunday.

The conservative leader added the U.K. would consider taking part in a U.S.-led military effort to bolster the Gulf kingdom’s defenses, while Iran’s president announced plans for a rival Iranian-led security coalition.

Britain had previously held back from attributing blame for the drone and missile attack. Saudi Arabia and the United States say Iran supplied 18 drones and seven cruise missiles which hit an oil field and processing facility, something Tehran denies.

Iran warned the U.S. that any military response will spark an “all-out war” with immediate retaliation from Tehran.

Secretary of State Mike Pompeo and Vice President Mike Pence both condemned the attack on Saudi oil facilities as “an act of war.”

Speaking on board an RAF Voyager jet late Sunday on the way to the U.N. General Assembly in New York, Johnson said, “the U.K. is attributing responsibility with a very high degree of probability to Iran” for the attack by drones and cruise missiles.

“We will be working with our American friends and our European friends to construct a response that tries to de-escalate tensions in the Gulf region.”

Johnson confirmed he would meet Iranian President Hassan Rouhani at this week’s U.N. gathering. Johnson is also due to hold talks with U.S. President Donald Trump, German Chancellor Angela Merkel and French President Emmanuel Macron.

He said he wanted Britain to be “a bridge between our European friends and the Americans when it comes to the crisis in the Gulf.”

If diplomacy eventually fails, Johnson has not ruled out a more aggresive response.

The Trump administration announced Friday that it would send additional U.S. troops and missile defense equipment to Saudi Arabia and the United Arab Emirates as part of a “defensive” deployment.

Officials said the number of troops was likely to be in the hundreds, with Defense Secretary Mark Esper telling Pentagon reporters this is a first step to beef up security and he would not rule out additional moves down the road.

“We will be following that very closely,” Johnson said. “And clearly if we are asked, either by the Saudis or by the Americans, to have a role, then we will consider in what way we could be useful. We will consider in what way we could be useful, if asked, depending on what the exact plan is.”

AP contributed to this report