With the US midterm elections fast-approaching, voters are increasingly worried about the price of petrol.

American gas prices have soared by 36pc in the last month to surpass the painful threshold of $4 a gallon – a damning contradiction to Donald Trump’s central election campaign promise to bring down prices from “day one”.

But the president thinks he’s found the solution. Asked how he would bring down rising oil and petrol prices, he replied: “All I have to do is leave Iran. And I will be doing that very soon.”

The price of Brent crude plunged to near $100 per barrel following the comments Trump made in the Oval Office on Tuesday night, dropping from a high of $119 reached earlier on Tuesday.

But anyone hoping for a quick end to the global energy crisis faces disappointment. Iranian control of the Strait of Hormuz, war damage to key infrastructure, high insurance premiums and the time it takes to restart trade mean we are likely to be stuck with $100 oil for a while.

It is a far cry from the $73 a barrel it was trading at before the US and Israel began their strikes – and means petrol and diesel prices will stay higher.

A key problem is that the president has limited power to reopen the Strait of Hormuz, through which a fifth of the world’s oil and gas supplies flow.

Iran’s blockade is currently robbing the world of 13 million barrels of oil per day, marking the biggest energy supply shock in history. What’s more, Tehran has made clear it will not easily relinquish its stranglehold over the market.

Ebrahim Azizi, the head of the Iranian parliament’s national security committee, said on Wednesday that the Strait would only reopen to “friendly” nations and ships that pay a £1.5m fee. This alone adds $1 to the cost of every barrel of oil.

At the same time, Gulf states need time to repair damaged energy infrastructure and reopen shuttered oil wells, which will take months. At Qatar’s Ras Laffan gas plant, which produces a fifth of the world’s liquefied natural gas (LNG), officials have warned it will take three to five years to repair missile damage.

Meanwhile, ships will take months to reroute. And the war has revealed a structural risk from high dependence on Gulf oil, which means that countries will build even larger strategic reserves, further increasing demand pressures.

For those vessels that do head to the Gulf, they are likely to face higher insurance costs than before. Premiums have surged since the start of the conflict for understandable reasons.

Yet there is no guarantee they will fall back if it ends. Convincing insurers to cut their war risk surcharges will take much more than social media posts from Trump. Lingering risk premiums and restrictions will continue to keep vessels away from the Middle East even if the Strait of Hormuz reopens unconditionally, warns June Goh, a Sparta Commodities analyst.

Even if Trump declares peace tonight, Ole Hansen, head of commodity strategy at Saxo Bank, believes oil prices will not get back to where they were before the conflict began.

“A while back, I stopped listening to what Trump says,” he explains. “Ultimately, Iran unfortunately holds the key and so far they have been showing no interest in using this key to unlock the Strait of Hormuz.”

He expects global supply to be constrained for three to six months.

“That means we’re going to go through a period with high prices. I will be surprised if we see Brent come back to $90 during this time and probably closer to $100 would make more sense, simply because of the imbalance that it will take months to rectify.”

Beyond that, oil prices are unlikely to fall below $80 for years. “If $70 was the old normal, I would imagine the new normal is probably closer to somewhere between $80 and $90.”

SEB, a Norwegian corporate bank, expects oil to average $100 for the rest of the year, even assuming flow out of the Gulf returns to normal levels by mid-May.

It’s not just oil: European gas prices have also risen by more than 60pc since the end of February.

The jump and disruption to supply have prompted countries to run down emergency stockpiles.

But they will now be forced to rebuild these buffers ahead of next winter. That means there will be a scramble for supply just as Asia enters its peak gas use period over summer, when air conditioners are fired up across the continent to combat sweltering temperatures.

“If we get a solution today, it doesn’t remove the fact that supplies into the global market have built up a massive deficit over the past month and we have a market where it will take time before production equals demand,” says Hansen.

There is an added risk that Iran will feel emboldened if Trump pulls out of the war without a deal.

As an oil exporter, Tehran benefits hugely from higher oil prices. Choking off supplies through the Strait of Hormuz would therefore refill Iran’s coffers, and deal a blow to Trump.

“The smart thing to do, of course, would be for them to play to just get rich,” says Bjarne Schieldrop, chief commodities analyst at SEB.

“And the easy way of hitting back at Trump, if Iran is going to be vindictive, is elevated oil prices ahead of the midterm elections.”

Trump can promise lower oil prices as much as he likes, but only a radical reduction in demand or a huge increase in global supply will bring them back to where they were just over a month ago. And neither of those outcomes look likely in the short-term.

“Getting back to where we came before the midterms would be wishful thinking,” says Hansen.

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