CENTCOM says helicopter fired at engine room of Panama-flagged Vela Nova as US-Iran diplomacy remains stalled.

The United States military has said it fired on a ship attempting to break its blockade of Iranian ports in the Gulf of Oman.

The attack on Tuesday comes amid a period of relative calm in the US-Israeli war with Iran, with attacks mostly paused since a 13-day escalation in July. That came after a ceasefire as part of a Memorandum of Understanding (MoU) signed by the US and Iran in June appeared to collapse.

In a statement, US Central Command (CENTCOM), which oversees the Middle East, said a Navy helicopter fired two Hellfire missiles at the Panama-flagged Vela Nova cargo vessel.

It said the vessel “attempted to transit the Gulf of Oman and violate the U.S. blockade against Iran by sailing toward an Iranian port”.

The attack targeted the ship’s engine room and disabled its steering gear, CENTCOM said, alleging the crew “ignored repeated warnings from American forces”.

It did not say if any crew members were wounded in the attack. In its statement on Tuesday, CENTCOM said US forces had disabled 55 commercial vessels throughout its blockade on Iranian ports, disabled three “non-compliant vessels”, and boarded two.

The US reimposed its naval blockade of Iranian ports amid the recent return to fighting, with Iran again reasserting its control over the Strait of Hormuz. Both of those conditions had been lifted as part of the June MoU, which was meant to launch renewed negotiations on a more lasting peace, as well as the future of crippling sanctions on Iran and its nuclear programme.

Efforts to return to an agreement have so far yielded little progress, with Trump on Monday appearing to up the ante as he called for reparations from Iran for “50 years” of damage. Tehran has previously called for reconstruction funding to be part of any deal, with the June MoU containing a preliminary plan for a $300bn fund.

The conflict has been further complicated in the latest bout of fighting by attacks by the Yemen-based Houthis on ships in the Bab al-Mandeb Strait, another key trade route in the region.

Iran, for its part, has largely focused its diplomatic efforts on direct talks with Oman to determine new shipping lines in the Strait of Hormuz, an arterial waterway through which 20 percent of the world’s maritime fossil fuel trade transited prior to the war launched by the US and Israel on February 28.

Iran’s semi-official Tasnim news agency on Tuesday quoted Mohsen Rezaei, secretary of Iran’s Supreme National Security Council, saying the Strait of Hormuz “will not be opened until the United States changes its behaviour and accepts Iran’s conditions”.

He maintained that any agreement with Oman would be “separate” from the issue of the strait’s closure.

Pakistan’s Interior Minister Mohsin Naqvi, meanwhile, arrived in Tehran on Tuesday for talks with Iranian officials, in the latest effort towards wider mediation of the war.