Iran has once again closed the Strait of Hormuz, declaring the move a direct response to what it describes as an ongoing United States blockade of Iranian ports — casting fresh doubt over fragile diplomatic efforts to end the US-Israel war on Iran.

Closure Follows Brief Reopening

The Iranian military announced on Saturday that control over the strategic waterway had "returned to its previous state", just hours after it had been reopened following a US-mediated ten-day ceasefire agreement between Israel and Lebanon. During the brief window of access, more than a dozen commercial vessels passed through the strait before the closure was reimposed.

Reports emerged of Iranian gunboats opening fire on a merchant ship that attempted to transit the waterway after the closure was declared. By 10:30 GMT on Saturday, at least eight oil and gas tankers had made it through, but roughly as many vessels appeared to have reversed course after initially heading toward the Gulf, according to the AFP news agency.

IRGC Issues Warning

The Islamic Revolutionary Guard Corps (IRGC) issued a statement carried by Iranian state media, describing the US blockade of Iranian ports as "acts of piracy and maritime theft". The IRGC added that the Strait of Hormuz is now "under the strict management and control of the armed forces".

"Until the US restores full freedom of navigation for vessels travelling from Iran to their destinations and back, the status of the Strait of Hormuz will remain tightly controlled and in its previous condition," the statement read.

The strait is one of the world's most critical chokepoints for energy supplies, with approximately 20 percent of global oil passing through it.

Trump's Optimism Undermined

The renewed closure directly contradicted the optimism expressed by US President Donald Trump just a day earlier, when he declared that a peace deal was "very close". Trump had welcomed the initial reopening of the strait on Friday but warned that US military strikes would resume if Iran did not agree to a broader deal encompassing its nuclear programme.

"Maybe I won't extend it," Trump told reporters aboard Air Force One, referring to the temporary ceasefire. "So you'll have a blockade, and unfortunately we'll have to start dropping bombs again." When pressed on whether a deal could be reached quickly, Trump said: "I think it's going to happen."

Iran, however, denied that any date had been set for further negotiations, accusing Washington of "betraying" diplomacy throughout the talks.

Confusion on the Water

Maritime shipping specialist John-Paul Rodrigue of Texas A&M University told Al Jazeera that contradictory signals from all sides had left vessel operators uncertain about whether it was safe to proceed.

"Ships have been attempting transit since the announcement, but it looks like many of them are heading back because the situation is unclear. There is contradictory information being issued by all parties," Rodrigue said.

Al Jazeera's correspondent reporting from Tehran, Tohid Asadi, described the overall situation as one defined by uncertainty, noting that Iran's demands extend well beyond the strait itself — encompassing security guarantees, sanctions relief, the unfreezing of assets, regional stability and resolution of the nuclear file.

With no confirmed date for a new round of talks and ships continuing to turn back from the strait, the path to any durable agreement remains deeply unclear.