President Donald Trump declared the return of a US naval blockade on Iranian ports on Monday, saying Washington would impose hefty fees on ships transiting the Strait of Hormuz as fighting once again flared over the vital waterway.
Iran's military command, however, insisted it would not allow the US to "interfere" in the key conduit for oil and gas.
The competing claims came as the two sides traded attacks of a scale unseen since an April ceasefire. The US military said it hit dozens of targets on Monday, while Iran's Revolutionary Guards announced new strikes in response on Bahrain, Jordan, Kuwait and Oman.
The Strait of Hormuz was not an issue before the United States and Israel began their war with Iran in February, and passage through it was free, but Tehran subsequently blocked the waterway and now sees it as essential leverage over Washington.
The US has vehemently opposed Tehran's desire to charge tolls in the strait, which international law generally forbids, but on Monday, Trump flipped the script and declared that Washington itself would collect fees.
In a post on his Truth Social site, Trump declared that the US would be "known as 'THE GUARDIAN OF THE HORMUZ STRAIT'," and "be reimbursed, at the rate of 20% on all cargo shipped, for any and all costs necessary to do the job of providing safety and security to this very volatile section of the World".
While Iran's ports would again be blockaded, he said, "all other countries will have fair and open use of the strait".
The spokesman for Iran's Khatam Al-Anbiya military command, however, insisted that Tehran "under no circumstances will allow... the United States to interfere in the management" of the strategic waterway.
- 'In crisis' -
Despite last week declaring the ceasefire with Iran over, Trump has said negotiations aimed at finding a permanent settlement would continue.
He told Fox News that there were hours of talks on Sunday, but accused Iranian negotiators of going back on what they had agreed.
Iran's foreign ministry spokesman Esmaeil Baqaei said earlier on Monday that the June memorandum of understanding that formed the basis for the negotiations and lifted the US blockade was "in crisis".
The previous blockade, in place from April to June, cut off Iranian oil exports and threatened a damaging shutdown of the industry.
Baqaei said Iran would ignore its obligations under the deal if the US did the same, but nonetheless added that Tehran was continuing talks with mediators from Qatar, Pakistan and Oman in an effort to prevent further escalation.
The past week's hostilities have centered on the critical energy trade route, which Iran's Guards say is "closed".
On Monday, spokesman for the Guards Hossein Mohebi accused the US of endangering global oil and gas supplies by interfering in the strait, saying it "must be held accountable" while insisting on Tehran's sovereignty over Hormuz.
Amid the fighting, mediators have been trying to salvage a diplomatic resolution to the war.
Pakistan, a key intermediary in negotiations, expressed "deep concern at escalation in regional tensions", according to its foreign office.
But analyst Bader Al-Saif said the escalating attacks would merely delay a permanent agreement.
"Both sides want to end the impasse on their own terms, and they are increasingly finding it difficult to do so. Hence, the return to and increase in the scale of attacks," said Al-Saif, an associate fellow at Chatham House.
"That only prolongs what will eventually happen: a negotiated settlement."
- 'Heinous attacks' -
Iranian state media reported deaths in the latest US strikes, which it said targeted large areas across the south and west.
At least 25 people have been killed in Iran since hostilities resumed on Wednesday, according to an AFP tally based on Iranian announcements.
Iran's Revolutionary Guards said they had struck Jordan, Bahrain and Kuwait, state media reported on Monday.
Air raid alerts sounded in Bahrain, while Kuwait's army said the country's forces were intercepting "hostile aerial targets" on Monday.
Jordan's army said it had intercepted four Iranian missiles.
Bahrain's military accused Iran of committing "heinous attacks with missiles and drones that target civilians", adding it had shot down a number of Iranian projectiles Monday morning.
