The price of oil is expected to soar on Monday despite a pledge by major oil-producing nations to increase production as the US-Israel war on Iran and effective closure of the strait of Hormuz rattle investors.

US crude oil is on track to rise by 9% when trading resumes, according to data from the broker IG. The jump comes despite Opec+, the cartel of oil producers, agreeing on Sunday to step up oil output by more than expected to counter the impact of the conflict.

Iran’s Revolutionary Guards reportedly told ships that passage through the strait of Hormuz was “not allowed” on Saturday, effectively shutting the key oil choke point and prompting the halt of some oil shipments.

A tanker in the strait was attacked on Sunday, and at least 150 tankers carrying crude, liquified natural gas and oil products dropped anchor in open waters across the Middle East gulf past the strait of Hormuz, Reuters reported.

Tehran has long warned that it could use its location to shut the strait in retaliation against military aggression. Tamsin Hunt, a senior analyst at S-RM, a global intelligence and cybersecurity consultancy, said that “closing the strait in full would be devastating for Iran’s own economy”.

IG’s weekend markets showed that US crude oil could rise to more than $73 (£54) a barrel when trading resumes in New York late on Sunday, up from $67 a barrel on Friday night. That would be its highest level since June 2025, when the US launched strikes on Iran’s nuclear facilities.

Analysts at Barclays said the oil price could reach $80 a barrel in the event of a “material supply disruption”.

Royal Bank of Canada analysts said: “It is our understanding that regional leaders warned Washington about the contagion risks of another confrontation with Iran and indicated that $100-plus oil was a clear and present danger.”

A jump in wholesale oil prices is expected to feed through to prices at the pump. The average UK price of petrol is 132.9p a litre, and diesel 142.4p, the AA said, warning that the Iran disruption could combine with the Treasury’s upcoming reversal of a 5p-a-litre fuel duty cut to push up prices.

In London, the FTSE 100, which hit a record high on Friday and had been close to breaking 11,000 for the first time, is expected to fall by about 0.5% on Monday morning.

Global investors are expected to seek out safe-haven assets on Monday. Gold, which has risen for the past four weeks, is up 2.25% to almost $5,400 an ounce on IG’s weekend markets, and silver is trading 3.2% higher.

About a fifth of global oil consumption passes through the strait of Hormuz, and a closure would disrupt shipments from Saudi Arabia, the United Arab Emirates, Iraq and Kuwait as well as from Iran, leading to shortages and higher energy prices.

Eight Opec+ countries agreed in principle at Sunday’s meeting to raise oil output by 206,000 barrels a day in April, compared with the original expectations of a 137,000 rise, Reuters reported.

The ports company DP World said it had suspended operations at the Jebel Ali port in Dubai and the Mediterranean Shipping Company stopped booking for worldwide cargo into the Middle East until further notice.

The International Energy Agency said it was actively monitoring events in the Middle East and the potential implications for global oil and gas markets and trade flows.

The conflict has also driven up the cost of insuring ships in the region, according to Dylan Mortimer, the marine hull UK war leader at the risk management consultancy Marsh.

“The primary risks centre on the Persian and Arabian Gulf, particularly the threat of vessel boarding and seizure by Iranian forces and the potential closure of the strait of Hormuz,” he said.

Oman said on Sunday that an oil tanker in the strait of Hormuz came under attack, injuring four mariners onboard. The attack targeted a vessel registered in the Pacific island nation of Palau, the state-run Oman news agency said.

Mortimer said attacks on shipping could have “major repercussions across war insurance rates”, adding: “Crew are far more likely to be concerned than they might have been to previous risks. The situation remains very fluid, requiring ongoing attention.”

Most stock markets in the Gulf region fell on Sunday. Saudi Arabia’s market lost 2.5%, pulled down by financial stocks, industrial companies and utilities, but Saudi Aramco’s shares rose by 2.5% following the forecast of a jump in the price of crude.

Kuwait’s stock exchange suspended trade until further notice, citing the “exceptional circumstances” the country was facing.