President Donald Trump has announced the US will help "guide" ships that have been stranded by Iran's closure of the Strait of Hormuz.

The Strait has remained largely blocked since the US and Israel launched air strikes on Iran - and Tehran responded by blocking the crucial waterway through which 20% of the world's oil and liquefied natural gas is meant to pass freely.

The day after the announcement, limited fighting appears to have resumed, with the US striking several Iranian small boats and Iran reportedly launching a series of attacks of its own.

What does Trump's "Project Freedom" entail and could it lead to a wider resumption of hostilities?

The president said the US had been asked by countries "from all over the World" to help free up their ships which were "locked up in the Strait of Hormuz" and were "merely neutral and innocent bystanders!".

And so, in response, the US would "guide their Ships safely out of these restricted Waterways".

"The Ship movement is merely meant to free up people, companies, and Countries that have done absolutely nothing wrong — They are victims of circumstance," Trump said in the post on his Truth Social platform.

He added this was "a Humanitarian gesture on behalf of the United States, Middle Eastern Countries but, in particular, the Country of Iran" - as many of these vessels were "running low on food, and everything else necessary for largescale crews to stay on board in a healthy and sanitary manner".

Trump's announcement appears mild compared to previous statements against Iran.

It even makes it sound like Iran is a party to the operation - the president went as far as to say "Project Freedom" was being undertaken on behalf of Iran, too.

But that is not how Iran sees the operation.

A statement from the head of Iran's central command said it would attack "any foreign armed force" that tried to approach or enter the Strait, "especially, the aggressive US army".

Maj Gen Ali Abdollahi said safe passage through it must be co-ordinated with Iran "under all circumstances".

An estimated 20,000 sailors and 2,000 ships have been trapped in the Gulf since the start of the war with Iran, according to the International Maritime Organisation - a UN agency that regulates shipping.

There has been growing concern over dwindling supplies and the effects on sailors' physical and mental health.

But Trump did not say how they would be able to sail away - he only threatened to use force "if, in any way, this Humanitarian process is interfered with".

Hours later, US Central Command (Centcom) announced that "guided-missile destroyers, over 100 land and sea-based aircraft, multi-domain unmanned platforms, and 15,000 service members" would be used to support the operation.

In a briefing, Centcom commander Adm Brad Cooper said that some of the attack helicopters supporting the mission were used to sink six small Iranian boats that were targeting civilian vessels.

Adm Cooper added that "we will shoot" at any Iranian vessels deemed to be interfering with the broader effort to help ships pass through the area.

There has been relatively sparse detail released on what the broader operation will look like, although Cooper explained it would ultimately establish a two-way path in the waterway.

If the US guidance was meant to offer information and advice to vessels and crew, that may be of little help given Iran's ominous threats to attack them.

If, on the other hand, the US will attempt to provide stricken ships with a military escort, that could bring them back into direct military confrontation with Iran.

Cooper said that the effort includes a "much broader defensive package" than would be required solely to escort ships.

Mick Mulroy, a former deputy assistant secretary of defence for the Middle East and a veteran of both the Marine Corps and the CIA's paramilitary wing, told the BBC he believes that Project Freedom will be focused on providing air cover and defense from missile and drone attacks - rather than a physical escort of those vessels through the Strait of Hormuz.

However, Mulroy said there is no guarantee it will be successful in helping restore freedom of movement and commerce in the strait.

"The question is whether ships will trust their ability to get through without being attacked, and more importantly, the insurance company," he said.

"If not, the effort will not have the impact we hoped."

The American military says it is implementing Trump's plan.

On Monday afternoon, Centcom said US Navy guided-missile destroyers were operating in the Gulf "after transiting the Strait of Hormuz in support of Project Freedom".

It added American forces were "actively assisting efforts to restore transit for commercial shipping" but gave no details.

"As a first step, 2 U.S.-flagged merchant vessels have successfully transited through the Strait of Hormuz and are safely headed on their journey," Centcom also said. Again, no details were released about the identity of the commercial vessels.

The BBC could not immediately see any vessels matching the US description on the tracking site MarineTraffic. It is also possible for vessels to turn off their location transmissions or to falsify them.

Iran's powerful Islamic Revolutionary Guard Corps denied any vessels had passed through the Strait. It said the US statements were "baseless and entirely false" and warned that any other movements opposing the instructions of the IRGC Navy "face serious risks".

Grant Rumley, a Middle East expert who served as an advisor to both the Biden and Trump White Houses between 2018 and 2021, said that securing passage for all the ships in the Gulf would be "very, very hard".

Doing so may require a stronger, more "kinetic" military option - a possibility he views as likely.

"I think that the general consensus is that a resumption of hostilities is a question of when," he said. "Not if."

Hours after the US operation was meant to have begun, the Iranian military said: "With a firm and swift warning from the Islamic Republic Navy, the entry of American and Zionist enemy destroyers into the Strait of Hormuz was prevented."

More details were provided later by Iranian state media. It reported that the Iranian Army Navy had "issued a warning and fired warning shots along the route of the hostile enemy destroyers" - which the Americans had "disregarded".

Centcom quickly denied the Iranian claims that one of its warships had been hit by two missiles.

According to Centcom, Iran did fire cruise missiles at both US warships and US-flagged commercial ships, while drones and small boats were used against commercial ships.

In a post on Truth Social, Trump accused Iran of having "taken some shots" at "unrelated nations", prompting the US strikes on small boats.

The United Arab Emirates (UAE) - a Gulf ally of the US, which has often been attacked by Iran during the war - said a tanker affiliated with Adnoc, its state-owned oil company, had been targeted by two drones as it transited the Strait of Hormuz.

No-one was injured, the country's foreign ministry said in a statement. At least three missile interceptions were also reported.

A suspected strike also hit a South Korean cargo vessel anchored in the Strait of Hormuz, in waters near the UAE, Trump said in his post.