FACT FOCUS: A look at US and Iranian claims of control over the Strait of Hormuz

A focal point of the Iran war is increasingly about who controls the Strait of Hormuz — a narrow, elbow-shaped waterway that for decades was a relatively safe and reliable transit route for Middle East oil and natural gas supplies.By saying that an interim ceasefire gave it the right to establish the terms under which ships traversed the strait, and threatening and firing upon vessels that did not use its preferred route, Iran has sought to exert control over the waterway and gain negotiating leverage with the United States.On Monday, President Donald Trump sought to tip the scales.

He reimposed a blockade on Iran and said the U.S. controls the strait and would charge fees to ships for safe passage — essentially borrowing from the Iranian playbook.

The announcement came as the U.S. and Iran have been ramping up attacks against each other to assert control over the strait, threatening a return to all-out war.

The world has long considered the strait — which passes the coastlines of Iran and Oman — a free-to-use, international waterway. But soon after it was attacked by the U.S.

and Israel on Feb. 28, Iran claimed sovereignty over it, disrupting world energy markets and driving up prices. Here’s a closer look at the facts.

Both Iran and the US say they control the Strait of Hormuz In a posting on Truth Social on Monday, Trump said the U.S. "will be, from this point forward, known as THE GUARDIAN OF THE HORMUZ STRAIT."

Iran’s paramilitary Revolutionary Guard, which controls the Islamic Republic's ballistic missile arsenal, says Tehran controls the strait. "We will not allow a rogue and child-killing army from the other side of the world to continue its illegal interference in it,” the Guard said Sunday.According to the United Nations Convention on the Law of the Sea, established in 1982, no country has the right to claim international waters and all ships have the right of unimpeded passage.

Even though the U.S. and Iran haven't ratified the convention, “that doesn’t matter, because this has become part of universal custom, so all states can rely on it under all circumstances,” said Marc Weller, director of the International Law Program at the University of Cambridge.

Still, both Iran and the U.S. have been using tools to exert control over the strait and constrain traffic.

“You have two nations, both of which are very capable — the U.S., because it has the most powerful Navy in the world, and Iran, which is geographically well positioned to disrupt commerce throughout the Strait of Hormuz — (and) can exercise a significant degree of control,” said Raymond Waid, who leads the maritime industry group at law firm Liskow & Lewis in New Orleans and a former Navy officer.

Maritime data agency Kpler said crossings declined by around 52% between Friday and Monday compared with the same period a week ago. About 14 ships passed through the strait on Sunday; before the war, about 130 ships passed through the strait daily. Iran says it has made ‘sincere’ efforts to ensure safe shipping The ability to disrupt shipping in the strait gives Iran leverage over the global economy.

Tehran used this leverage early in the war by attacking transiting ships and demanding payment in some cases to allow vessels through. Just the fear of being attacked by Iranian drones or speedboats was enough to deter ship traffic. After an interim ceasefire was announced last month, Iran insisted that ships register with the recently created Persian Gulf Strait Authority to have their crews and cargo vetted.

Iran also is demanding that ships only use a route near its coastline instead of a southern route along the coast of Oman, where the U.S. military had started guiding ships through.

The central part of the strait has been mined by Iran, so few vessels have tried to pass using that route.Tehran is suspected of attacking ships that have used the Oman route. The United Kingdom Maritime Trade Operations Center, which issues maritime security alerts, said it received reports of six ships attacked in the strait near Oman since June 25.

Iranian officials assert the right to manage traffic through the strait Washington and Tehran have debated what they agreed to regarding the strait. U.S.

officials say the interim agreement signed last month called for the strait to be reopened while a more permanent resolution to the war was negotiated.Iranian officials have said a clause in the interim deal gave them the right to manage ship traffic and that, so long as they didn't charge fees for 60 days, it was up to them to decide operating conditions.The interim agreement stated that Iran will “make arrangements using its best efforts for the safe passage of commercial vessels with no charge for 60 days only from the Persian Gulf to the Sea of Oman and vice versa.

“ It also called for Iran to ”conduct dialog with the Sultanate of Oman to define the future administration and maritime services in the strait.” The US now says it will charge a fee for safe passage The U.S.