As questions swirl over the Saudi oil attacks, all eyes are on the Middle East to see if tensions finally boil over.

United Nations – Many questions remain unanswered about the predawn attacks on Saudi Arabian oil facilities that sent crude prices skyrocketing, but perhaps the most pressing is whether the trigger will be pulled on a military response.

United Nations peace envoy to Yemen Martin Griffiths outlined on Monday the “terrifying” prospect of the attacks sparking a broader conflict in the powder-keg region.

“At a minimum, this kind of action carries the risk of dragging Yemen into a regional conflagration,” Griffiths told the UN Security Council via a video-link.

“Because of one thing we can be certain, and that is that this very serious incident makes the chances of a regional conflict that much higher.”

The strikes on Saudi Aramco petroleum and gas processing plants at Abqaiq and Khurais in the kingdom’s Eastern Province halted more than half of crude output from the world’s main exporter, by some 5.7 million barrels per day.

The Iran-aligned Houthi rebel movement in neighbouring Yemen, which has been fighting a Saudi-led coalition there since 2015, said it was behind the attacks and warned on Monday of continued drone and missile attacks on the kingdom.

US Secretary of State Mike Pompeo swiftly blamed Iran for the attacks, without offering evidence – a claim swiftly rebuffed by Tehran, which insisted it was not responsible.

The rapid developments have revived fears of fighting between Iranian and American forces in the Gulf.

Whodunnit?

For Justin Bronk, the author of a report on drone use by the Houthis and others in the Middle East for the Royal United Services Institute, a UK military think tank, the size of some of the blast holes on supplied photos of the smouldering plants may suggest cruise missile attacks, which would indicate Iranian involvement.

He hypothesised about a joint Houthi-Iran combined drone and missile assault launched from Yemen.

Other military analysts have speculated about launch sites by Iran-linked militias in Iraq.

Saturday’s attacks were the latest in a series of escalatory moves witnessed since the US unilaterally withdrew from a nuclear deal with Iran and other world powers in May 2018 and slapped sanctions on Iran’s oil and banking sectors in a “maximum pressure” campaign against it.

Iran has rolled back its commitments under the nuclear deal, while attacks on a Saudi oil pipeline and tankers off the UAE coast in May this year were linked by the US to Iran and Yemen’s Houthis.

But tensions seemed to be thawing in recent weeks, with US President Donald Trump dangling the prospect of some sanctions relief for Iran and a meeting with his Iranian counterpart Hassan Rouhani during the UN General Assembly in New York later this month.

Such a meeting is now unlikely.

Eckart Woertz, an expert on Gulf security and energy markets at the Barcelona Centre for International Affairs, a think tank, said the attacks appeared to deviate from Iran’s playbook.

“This was not just a proxy group bombing a pipeline that could be quickly repaired, this was a very central piece of Saudi infrastructure,” Woertz told Al Jazeera.

“Until now, the Iranians had played their escalation adroitly. But this was such an extraordinary escalation that Trump would have little choice but to retaliate. What is Iran’s calculation here, and do they have a Plan B?”

‘Ratchet up pressure’

Bronk, however, pointed to Trump’s stated unwillingness to go to war, his recent decision to sack his hawkish, anti-Iran national security adviser, John Bolton, and the president’s bid to win re-election in 2020 from voters who are still weary from wars in Iraq and Afghanistan.

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“The Iranian calculation is that the West doesn’t want to go to war in Iran. That Europe and the US are divided on Iran, that Trump is conflict-averse, and the Iranians need to keep the issue on the boil,” Bronk told Al Jazeera.

“Continuing to ratchet up the pressure is in Iran’s interests as long as it doesn’t lead to war, especially if the attack is de facto tied to Iran but cannot or will not be specifically attributed to the Islamic republic.”

For Jim Krane, author of Energy Kingdoms and a research analyst on the Gulf at Rice University, the attacks should serve as a wake-up call for world powers to broker an end to Yemen’s civil war.

Saudi Arabia and the UAE have led a military coalition against the Houthis and in support of the government of Yemen’s President Abd-Rabbu Mansour Hadi, resulting in what the UN calls the world’s worst humanitarian disaster.

“This is all a spin-off of this disastrous war in Yemen and hopefully, it will make the world pay more attention to a conflict in which coalition bombardments have killed thousands of people while Saudi Arabia has not seen much blowback,” Krane told Al Jazeera.

“We’re at a dangerous inflexion point. Either these attacks in Saudi will spur stronger calls for a settlement of the Yemen war, or they could push Saudi and Iran into a direct conflict that sucks in the US.”

Trump repeated again on Monday he wants to avoid a war in the Middle East. In June, after Tehran shot down a US drone, Trump ordered a retaliatory bombing raid against Iran, but called off the attack for fear of potential casualties, he said at the time.

However, Trump has said he is “locked and loaded” to respond to attacks on the Saudi oil plants. So will the commander-in-chief shoot?

“Locked and loaded to do what?” asked Bronk.

“Could the US do a load of damage to Iranian facilities in relatively short order? Yes. Would that lead to a horrendous spiral of escalation across the Middle East that the Trump administration is not prepared for? Yes.”