Strait of Hormuz: Here's why Iran might close this crucial waterway - and how
Just 24 miles wide at its narrowest point, the Strait of Hormuz is a crucial waterway through which millions of barrels of oil pass every day. Iran has repeatedly threatened to close it - is Tehran serious this time?
Monday 23 June 2025 18:18, UK
Every day, 21 million barrels of oil pass through the Strait of Hormuz, a narrow channel in the Middle East that is crucial to global trade. Now Iranian politicians want to block it, potentially sending energy prices surging.
The world is waiting for Iran's response to the recent US and Israeli strikes on its nuclear facilities, with fears the conflict could escalate in the volatile region.
One possibility is that Tehran could attempt to close the strategically vital Strait of Hormuz - and the Iranian parliament has voted to do just that.
US Secretary of State Marco Rubio warned it would be "economic suicide" for Iran to close the waterway, but it's possible that Iran decides to try it anyway in a bid to strike back at the West.
What is the Strait of Hormuz?
The Strait of Hormuz is a narrow passage that leads from the Persian Gulf to the Arabian Sea and the ocean beyond.
It's about 100 miles long and just 24 miles wide at its narrowest point.
For countries like Kuwait, Bahrain, Qatar and the UAE along the southern side of the strait - producers of a significant portion of the world's oil - it's the only access to the sea, making it one of the most strategically important choke points in global trade.
On the northern bank, the coastline is dominated by Iran, which has repeatedly threatened to exert control over the strait.
Why is it important?
"The Strait of Hormuz sees an enormous amount of the world's traffic," says Dan Marks, an expert in energy security at the RUSI thinktank. "There's no alternative."
And the stats back it up. In 2024 and the first quarter of 2025, roughly 20% of global oil and petroleum products passed through the narrow waterway, according to the US government. The same was true for global liquified natural gas (LNG) last year.
Any disruption to the flow of oil transportation through the strait could send energy prices rising and cause huge shipping delays.
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Potential for real impact on UK economy
Like much of this conflict, the impact on the economy is uncertain.
It depends on how long it lasts and what comes next.
But the threat of the Strait of Hormuz being closed off is one that could have real impacts on the UK economy.
As the shipping lane is a vital route for oil and gas supplies, its closure could majorly disrupt the flow and delivery.
A fifth of global oil and about a quarter of natural gas is transported through the passage.
Were it to close, it could cause a price shock like the one in 2022 when Russia invaded Ukraine.
Those high prices filter through the economy, making production more expensive and pushing up prices at the till, petrol pump and in energy bills.
It was those high gas costs that sparked off the inflation spikes and cost of living crisis.
Is Iran going to try and close the Strait of Hormuz?
It's unclear. The Iranian parliament approved a motion to close the strait on Sunday, but it would need to be sanctioned by the country's security council before any action was taken.
"It's clearly something Iran thinks about," Mr Marks said, but added: "Closing the Strait of Hormuz is easier to threaten when Iran looks like a credible military threat.
"Now it looks potentially like a less credible threat... they don't have control of their airspace."
He said it is "most likely" that Iran does not move to block shipping through the strait, but said it could depend on what cost the regime is willing to pay.
How could Iran close the Strait of Hormuz?
If it does decide to try and limit or stop ships from moving through the chokepoint at the Strait of Hormuz, analysts say there are multiple ways Tehran could try to do so.
Iran has developed a "considerable array" of capabilities, including sea mines, fast attack vessels, submarines, drones and missile systems, Nick Childs, an expert in maritime security at the International Institute for Strategic Studies thinktank, says.
He added: "If used in a comprehensive campaign, these could cause very significant disruption and also potentially seriously hazard US and other naval units including mine countermeasures vessels seeking to keep the waterway open."
There's also the possibility that instead of closing the strait entirely, Iran could try and pursue a more targeted campaign of harassment against specific ships - perhaps Israeli, US or other Western vessels.
In 2019, the British-flagged Steno Impero ship was detained by Iran for more than two months in the Strait of Hormuz.
Indeed, there has already been heavy GPS jamming detected in the region since the start of the Iran-Israel conflict, though its origin is not clear.
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What would the response to Iran be?
A concerted Iranian attempt to shut the strait could provoke a "considerable and comprehensive US military response", Mr Childs said.
He added: "The Iranian forces could expect to suffer significant damage in return.
"The other deterrents to Iran are that a closure of the Strait of Hormuz would hit its own economy, affect one of Tehran's key supporters, China, which is a key customer for Iranian oil, and because the potential effects on the global economy would be most likely to provoke an international response not in Iran's favour."
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US Secretary of State Marco Rubio played down the threat to the strait.
"It's economic suicide for them if they do it. And we retain options to deal with that," he said.
Dan Marks from RUSI said there is "potential for miscalculation".
He added: "Overall it seems not in Iran or the Iranian leadership's interests to close the strait but I would say that that is very much looking at it from a Western lens, and the Iranian leadership will likely see it differently and that's when the risk of miscalculation comes in."