US President Donald Trump has appeared to signal a reset on war with Iran, saying there is “no time pressure” on the ceasefire or for further peace talks.

Trump made the comments to Fox News on Wednesday (US time), hours after Iran seized two ships in the Strait of Hormuz, tightening its grip on the strategic waterway.

Asked on Fox News when the US and Israeli war with Iran might end, Trump said there was “no time frame” and no rush. He has previously said it might last four to six weeks – it is now in its seventh.

“People say I want to get it over because of the midterms (US elections in November), not true,” Trump said, adding that his administration wanted to “get a good deal for the American people”.

Trump made what appeared to be a unilateral announcement on ‌Tuesday extending the ceasefire in the Middle East, hours after threatening renewed violence. He said it would run until talks on an Iranian proposal in peace talks.

But Iranian officials have not said they agree to any extension of the truce, and have criticised Trump’s decision to maintain the US Navy blockade of Iran’s trade by sea, which Tehran considers an act of war.

CNN reports that the Trump administration has had virtual silence from Iranian officials as late as Tuesday night, US time.

The White House continues to project control over the war, despite the Iranian negotiating team snubbing an offer of a second round of talks planned for the Pakistani capital of Islamabad on Wednesday.

White House press secretary Karoline Leavitt said Trump was “generously offering a bit of flexibility to a regime who has been completely tarnished”, referring to the ceasefire extension.

“This is a battle between the pragmatists and the hard-liners in Iran right now, and the President wants a unified response,” she said.

She said the blockade was hurting Iran.

“They can’t even pay their own people as a result of this economic leverage that President Trump has inflicted over them,” Leavitt said.

“So he’s satisfied with that, as we await their response, and we will see.”

She also said Trump had given Iran no hard timelines.

“The President has not set a firm deadline to receive an Iranian proposal, unlike some of the reporting I’ve seen today. Ultimately the timeline will be dictated by the commander in chief,” she said.

Iran has also condemned the US Navy’s interception of its ships at sea as part of its blockade. One was an Iranian cargo vessel, the other a huge tanker bound for Singapore that was boarded in the Indian Ocean on Tuesday hours ​before peace talks were due to resume.

Iran’s parliament speaker and lead negotiator Mohammad Baqer Qalibaf said a full ceasefire made sense only if the blockade of the Strait of Hormuz was lifted.

He said reopening the waterway – which usually carries a fifth of the world’s oil trade – was impossible with such a “flagrant breach of the ceasefire”, Qalibaf said on social media.

“You did not achieve your goals through military aggression and you will not achieve them by bullying either,” he wrote in his first response to Trump’s announcement.

“The only way is recognising the Iranian people’s rights.”

The Islamic Revolutionary Guards Corps seized ​two vessels for what it called maritime violations and escorted them to Iranian shores, according to statements by the shipping companies and Iran’s semi-official Tasnim news agency. It was the first time Iran has seized ships since the war began at the end of February.

Iranian news outlet Tasnim later posted dramatic footage of Iranian commandos raiding the two ships.

Trump this week again backed away at the last moment from repeated threats to bomb Iran’s power plants and other civilian infrastructure, which the United Nations and others warn would violate international humanitarian law. But little progress has been made in ending the war that started with joint US-Israeli attacks on Iran on February 28.

That leaves the two sides in a ‌holding pattern with the crucial Strait ‌of Hormuz still effectively shut, straining economies across the ⁠world.

Thousands of people have been killed across the Middle East, mostly in Iran and Lebanon, where the Iran-allied Hezbollah militant group joined the fighting against Israel.

Both Iran and the US-Israel alliance have continued to claim to be winning the war. Iran showcased some of its ballistic weapons at ​a parade in Tehran ‌on Tuesday night, with images on state TV showing large crowds waving Iranian flags and a banner in the background with a fist choking off the strait.

Before the war, about 130 vessels crossed the strait each day, a figure that has plummeted to just a handful since fighting began.

The US military said it had so far directed 31 vessels to turn around or return to port as part of the US blockade against Iran. Far beyond the Gulf, the US military has also intercepted at least three Iranian-flagged tankers in Asian waters, sources said, redirecting them away from their positions near India, Malaysia and Sri Lanka.

A first session of peace talks between Iran and the US in Islamabad 11 days ago produced no agreement.

-with AAP