The Islamic Republic has responded to the domestic unrest with unprecedented violence, killing thousands of people since protests began in late December.

Trump warned the regime not to kill the protesters and vowed that help was on the way. While he reportedly repelled an attack last month, the recent arrival of a US aircraft carrier in the Middle East has raised expectations that a strike is imminent.

“We put the 75% probability that in the coming days to weeks there will be some kind of attack by the US on Iran,” Bob McNally, Rapidan Energy Group founder and former White House energy advisor, told CNBC on Thursday.

Brent crude futures jumped 5% last week and 14% since the start of the year. Prices have now broken their annual pattern of a steady decline punctuated by brief spikes that quickly reverse to resume the downtrend, he said.

The US attack on Iran’s nuclear facilities last year only resulted in a temporary price increase as the conflict remained limited in scope and avoided the country’s oil infrastructure.

In addition, last month’s US military raid to arrest Venezuelan dictator Nicolas Maduro failed to move the needle in oil markets because production was not interrupted.

“But it’s a reality,” McNally warned. “Markets are pricing in the risk that this time the past doesn’t reflect the future—that we could have continued disruption of energy flows.”

Iran pumped 4.7 million barrels per day last year, accounting for 4.4% of the world’s oil supplies. Most of its authorized shipments go to China via a so-called shadow fleet.

But the bigger risk centers on the potential for Iran to close the Strait of Hormuz, through which a fifth of all the world’s oil and liquefied natural gas passes on its way to export markets.

Markets believed the US Navy could quickly clear any underwater mines or other threats that would prevent tankers from traversing the Strait of Hormuz, but McNally thought that was wrong.

He pointed out that the US has failed to completely alleviate the threat from the Houthi rebels, who attacked shipping in the Persian Gulf before Trump reached a ceasefire agreement.

“The Iranians have much better weapons and a much better coastline to harass in that strait, so God forbid that comes to that,” McNally added.

On Sunday, Iran’s supreme leader warned that any US attack would spark a “regional war” in the Mideast, marking the most direct threat he has made so far amid Trump’s military buildup in the area.

but Axios sources said that the Trump administration has told Tehran through back channels that it is open to meeting to negotiate a deal.

McNally on Thursday flagged the escalating rhetoric and highlighted the potential for chaos in the LNG market if there is an Iranian blockade of the strait.

“If it lasts more than a day or two, the market will be shocked because we cannot imagine a scenario where the US military does not dominate the military (and) for more than several hours in days,” he predicted. “We haven’t seen it historically, but it’s possible. In that case, you’ll see the mother of all bidding in any cargo area for LNG.”