“Oil policy was one of the instruments,” said Mustafa Alani, head of defense and security department at the Gulf Research Center. “The other thing is to counter Iranian investment in the region. Under King Salman it has become a clear-cut policy. There is no hesitation.”

Also last month, Saudi Arabia banned Iran’s Mahan Airline from flying through Saudi airspace. Shipping insurers and brokers have been advising clients since February that ships carrying Iranian crude will not be permitted to enter Saudi or Bahraini waters, according to an April report by Control Risks. It said ships that have been to Iran as one of their last three points of entry must also receive special approval.

Saudi rulers are complementing those efforts with attempts to deepen Iran’s political isolation in the Middle East.

Last month, Jordan recalled its ambassador to Iran shortly after a visit by the Saudi deputy crown prince. Ten days later, it signed an accord that could pave the way for multi-billion-dollar Saudi investments. In February, the kingdom scrapped a $3 billion deal to supply much-needed weapons to the Lebanese military, citing the rising influence of Hezbollah, a militant group backed by Tehran.

The Saudi moves take place against the backdrop of cooler ties with the U.S., in part because of the Iranian nuclear deal. In interviews published by The Atlantic magazine, President Barack Obama said the Saudis must “share” their region with Iran, and was reported describing the U.S. relationship with the kingdom as “complicated.”

The Saudi push is a “patchwork campaign,” Shashank Joshi, a senior research fellow at the Royal United Services Institute in London, said by phone. The Saudis can’t do much to block Iran at the global level, he said, but they’re “applying pressure on Iran wherever they are able to do so, to limit its political and economic influence.”

But one hurdle for the Saudis is that the other Gulf Cooperation Council states, key to the effort, may not be totally on board.

Bahrain was the only other country in the six-member GCC to follow the Saudis in cutting diplomatic ties this year. Kuwait recalled its ambassador to Tehran in January ans the United Arab Emirates reduced its diplomatic representation to the level of charge d’affaires.

The U.A.E has more at stake than the kingdom: Iran was its third largest trading partner in 2015, after India and China.

“We still see pretty substantial disagreements within the GCC,” Joshi said. “Iran is already integrated into the Gulf economic systems, and I don’t think anything Saudi Arabia can do can seriously disentangle that.”

David Fuller's view

We have long had religious wars in the Middle East and now we have oil wars as well.  The region’s two biggest powers – Saudi Arabia and Iran – are at the centre of this conflict, which can too easily rumble on for many more years.  It should remain largely regional, although as we know from 9/11 and the more recent Daesh brutality, this is not always the case.  

The much greater risk would be if either side, let alone both sides developed or acquired nuclear weapons.  Iraq was reportedly well on the way before President Obama’s sanctions led to an agreement to halt their nuclear development programme.  Saudi Arabia presumably lacks this nuclear capability but they could probably buy it in.

Please note: I will be leaving for an annual family holiday in Hay-on-Wye this Friday, and returning to Comment of the Day on Monday 13^th June.