President Donald Trump announced on Monday that the United States is reinstating its naval blockade of Iran and will levy a charge equivalent to 20 percent of the value of all cargo transiting the Strait of Hormuz. The declaration, made on social media and in a Fox News interview, came after a weekend of heavy US and Iranian military strikes across the Gulf and Tehran’s renewed closure of the strategic waterway. Global benchmark Brent crude jumped more than 4 percent on the news, while shipping data showed transits through the strait falling to their lowest level in five weeks.

From Washington’s perspective, the measures are a response to what Trump described as Iran’s violation of an interim agreement and its attacks on commercial vessels. “We are reinstating the Iranian Blockade, so named because it is only stopping Iran’s ships or customers from entering or leaving,” Trump wrote on Truth Social, adding that the US would henceforth be known as “the Guardian of the Hormuz Strait.” He said the 20 percent reimbursement would cover “any and all costs necessary to do the job of providing safety and security.” US Central Command confirmed that preparations to reimpose the blockade were under way, though military officials privately noted the operational challenges of enforcing a large-scale naval quarantine without a pre-existing formal plan.

Tehran immediately rejected the US claim to control the strait. The Khatam al-Anbiya joint military headquarters said it would not allow Washington to “interfere in the management” of the waterway and warned that any logistical cooperation with US forces would be considered an act of war against Iranian sovereignty. The Islamic Revolutionary Guard Corps maintained that the strait remains closed and that regular shipping would resume only once US military interventions cease. Iran’s foreign ministry, meanwhile, said it was in contact with mediators from Qatar, Pakistan and Oman to prevent a wider escalation, while insisting that it had never been the first to violate the June memorandum of understanding.

The imposition of a transit fee and the blockade’s return place further strain on an already fragile diplomatic framework. The interim deal signed in mid-June had temporarily reopened the strait and paused hostilities for 60 days of negotiations, but both sides now accuse the other of breaching its terms. The 20 percent charge, which according to Bloomberg calculations could amount to roughly $15 per barrel of oil, also raises legal questions: US Secretary of State Marco Rubio stated last month that “no country is allowed to charge tolls or fees on an international waterway.” With the 60-day negotiating window approaching its midpoint, the renewed military exchanges and competing claims over the strait leave the path to a permanent settlement deeply uncertain.