The Middle East is “on the cusp of an all-out major war” following news Iran has refused to rule out a retaliatory attack against Israel.

A possible strike would be a response to Jerusalem's alleged killing of Ismail Haniyeh, the political leader of Hamas in Iran’s capital Tehran, last month.

Iran’s foreign ministry spokesperson Nasser Kanani said in its response to pleas from the West not to retaliate: “Such demands lack political logic, are entirely contrary to the principles and rules of international law, and represent an excessive request”.

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The refusal marks an alarming moment of tension in the Middle East as Iran, a major international player with the eighth-largest army in the world, holds Israel responsible for the killing on its soil.

On Monday, it was reported that Iran’s President Masoud Pezeshkian said to UK Prime Minister Keir Starmer over the phone that wider Israeli attacks in the Middle East were “irresponsible” and criticised the West for its silence over “unprecedented inhumane crime” in Gaza.

The wider situation is now a tinderbox, one that Professor Anthony Glees of The University of Buckingham says is on the brink. “It's blindingly obvious that the Middle East is on the cusp of an all-out major war,” he said.

“But it is also obvious that it'd be a war none of the big players want and, above all, it's clear that the US is doing everything in its power to prevent that major war from breaking out.”

He feared the risk of an “error,” which could lead to escalation, noting: “We watch and wait with bated breath. It's a total cliffhanger. The chances of an error triggering a major conflagration have increased exponentially. [United States Secretary of State Anthony] Blinken has cancelled his trip to the region, always a bad, bad sign. But as I say, there's a glimmer of hope there. The next 24 hours will be critical.”

Despite this though, Prof Glees argued “there's still a chance that an all-out regional war can be avoided”.

He said the US would be doing all it could to diffuse the situation with a combination of shows of strength in the region to dissuade further escalation, coupled with efforts to orchestrate a ceasefire and “keep the lid on the pressure cooker”.

He said this double-pronged approach currently sees: “[US President Joe] Biden's White House telling Iran to back off, and telling Israel it will be covered and that Iran will be contained by US firepower.

“But secondly, at the same time, Biden is trying as hard as he can to get a cease-fire in Gaza and get the remaining living hostages returned to Israel.

“Biden's desperate last-chance saloon gamble here is that to achieve a cease-fire, effectively ending the awful Gazan war, would placate Iran, and give it a major diplomatic win. This would obviate any necessity to hit Israel.

"The talks are meant to start tomorrow in Dohar. If they go ahead we can breathe a small little breath of relief and Iran, too, may step back.

He said the decision to support a ceasefire could make sense for Iran as its “last attempt at 'punishing' Israel in April, when it fired 300 missiles and drones, was basically a massive flop, not least because the US and its allies, including the UK, prevented any serious damage being done".

He added: “On the other hand, it's a fact that Iran has suffered a deep and lasting blow to its status as the mothership of Islamism in the Middle East with the assassination of Hamas leader Ismail Haniyeh in Teheran, of all places which has following several high profile killings of Iranian generals in Syria and other Hamas leaders.

“The Iranian people will feel that Israel is provoking them with impunity and this is not a place [Iranian leadership] will want to be. They need to have something they can call 'revenge' and a ceasefire in Gaza could be it.”

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