The ceasefire in the Middle East is under threat as Iran accuses the US of “armed piracy” and denies any plan to join upcoming peace talks.

Tehran has also vowed to retaliate after the United States forcibly seized an Iranian-flagged cargo ship that tried to get around a naval blockade near the Strait of Hormuz.

US President Donald Trump said the USS Spruance, a US navy guided missile destroyer in the Gulf of Oman, stopped the Iranian vessel by blowing ‌a hole in its engine room.

“The US Navy Guided Missile Destroyer USS SPRUANCE intercepted the TOUSKA [ship] in the Gulf of Oman, and gave them fair warning to stop,” Trump wrote on social media.

“The Iranian crew refused to listen, so our Navy ship stopped them right in their tracks by blowing a hole in the engine room.”

The US Central Command said the Spruance had issued repeated warnings over a six-hour period. It released footage of Marines boarding the Touska.

“The TOUSKA is under US Treasury Sanctions because of their prior history of illegal activity,” Trump wrote.

On Monday, Australian time, Iran’s joint military ‌command, Khatam al-Anbiya, accused the ‌US of violating the 10-day-old ‌ceasefire in the region and vowed to retaliate.

State media ​quoted a Khatam al-Anbiya spokesperson as saying the ⁠vessel ‌was en ​route from China ​to Iran.

“We ‌warn that the ​armed forces of the Islamic Republic of Iran ​will ​soon ​respond and retaliate ‌against this armed piracy by the US military,” the spokesperson said.

News of the attack on an Iranian-flagged vessel threw into question Trump’s earlier announcement that US negotiators would head to Pakistan on Monday for another round of talks with Iran.

“My Representatives are going to Islamabad, Pakistan — They will be there tomorrow evening, for Negotiations,” he wrote on Truth Social.

He urged Iran to accept the US peace deal, vowing “No more Mr Nice Guy” if it did not – as well as issuing a fresh threat.

“We’re offering a very fair and reasonable DEAL, and I hope they take it because, if they don’t, the United States is going to knock out every single Power Plant, and every single Bridge, in Iran,” Trump wrote.

A White House official had said the US delegation would be headed by Vice President JD Vance, who led the war’s ‌first peace talks a week ago. Trump’s envoy Steve ⁠Witkoff and son-in-law Jared Kushner will also be there.

That had raised hopes of extending the fragile ceasefire that is set to expire by Wednesday. However, an Iranian state news agency reported Iranian officials had no plans to take part in the talks.

“Iran stated that its absence from the second round of talks stems from what it called ‌Washington’s excessive demands, unrealistic expectations, constant shifts in stance, repeated contradictions, and the ongoing naval blockade, which it considers a breach of the ceasefire,” Iran’s official IRNA news agency said.

Minutes after the ship seizure was announced, Iranian state media reported on President Masoud Pezeshkian’s phone conversation with Pakistani Prime Minister Shehbaz Sharif on Sunday.

US actions including bullying and unreasonable behaviour, have led to increased suspicion the US will repeat previous patterns and “betray diplomacy”, the reports cited Pezeshkian as saying.

Sharif’s office said Pezeshkian had thanked Pakistan for its mediation efforts, in ‌a readout of the call that ​made no mention of Iran rejecting the next round of talks.

Separately, Iran’s state broadcaster said Foreign Minister Abbas Araghchi told his Pakistani counterpart on a phone call that recent US actions, rhetoric and contradictions were signs of “bad intentions and lack of seriousness in diplomacy”.

The US has maintained its blockade of Iranian ports, while Iran has lifted and then reimposed its own blockade of marine traffic through the Strait of Hormuz, which before the war began almost two months ago handled roughly one-fifth of the world’s oil supply.

Iran’s chief negotiator, Mohammad Baqer Qalibaf, earlier said the two sides had made progress but were still far apart on nuclear issues and the Strait of Hormuz.

-with AAP