US Secretary of State Marco Rubio, concluding a tour of Gulf capitals, warned on Thursday that any Iranian attempt to impose transit fees on the Strait of Hormuz would risk “total chaos” and spread to other international waterways “like a contagion.” Speaking at a Gulf Cooperation Council meeting in Bahrain, Rubio reiterated Washington’s position that the strait is an international waterway not subject to any single state’s control. He also stressed that while the United States seeks a permanent peace accord with Iran following the signing of a 14-point memorandum of understanding on 17 June, it would not accept a deal “at any price” that undermined the security of its Gulf partners.

The remarks came hours after Iran’s Islamic Revolutionary Guard Corps (IRGC) issued a statement warning that any vessel crossing the strait without authorisation would be “dealt with” and that the only permissible route was the one announced by the Islamic Republic. The IRGC specifically denounced a temporary maritime corridor unveiled by Oman in coordination with the International Maritime Organisation, a UN agency, describing unauthorised passages as “unacceptable and extremely dangerous.” Tehran has framed its proposal for regional control of the strait—potentially including environmental and security service fees—as a matter of sovereignty, while its foreign ministry spokesman accused NATO of “complicity” in what it calls an “unlawful war” and described the initial ceasefire protocol as “a declaration of America’s defeat.”

Gulf states, which were struck by Iranian missiles and drones during the conflict that began on 28 February, have voiced deep unease about the trajectory of the US-Iran negotiations. Bahrain’s foreign minister, Abdullatif bin Rashid Al Zayani, spoke of “uncertainties” affecting the region. According to diplomats briefed on the discussions, Gulf capitals fear that a reconstruction fund worth an estimated $300 billion, included in the peace proposal, could allow Iran to rebuild its military capacity. They have insisted on being consulted at every stage of the talks. Oman’s announcement of a temporary shipping lane close to its coast, and Qatar’s prime minister travelling to Muscat to initiate broader discussions on the strait involving Gulf states, Iraq and Iran, reflect efforts by regional actors to shape the outcome.

The memorandum of understanding guarantees toll-free commercial transit for 60 days while technical negotiations continue, with the next round scheduled for 29 or 30 June in Switzerland. The dispute over Hormuz remains a central obstacle: Washington and its allies reject any fee structure, while Iran signals it will not relinquish the leverage it gained by blockading the waterway during the war. Oil prices have retreated to pre-war levels, with Brent crude trading around $72 a barrel, but the IRGC’s latest threats underscore the fragility of the ceasefire. The US Congress, meanwhile, is weighing an $88 billion supplemental funding request from the White House to cover war costs, even as lawmakers demand explicit authorisation for any future military action.