US President Donald Trump on Wednesday sharply escalated tensions with Iran, warning that the United States could launch another round of military strikes within hours after declaring that the ceasefire between the two countries was effectively over.

Speaking at the NATO Summit in Ankara, Turkey, Trump accused Tehran of continuing hostile actions and said Washington was prepared to respond with overwhelming force.

'We hit them very hard last night. Very, very hard. We'll probably hit them hard again tonight. I'll give them a little warning. We're going to hit them hard tonight,' Trump said while addressing reporters on the sidelines of the summit.

The Republican leader claimed Iran had carried out attacks on American military facilities in the Gulf and had also targeted ships using drones and missiles.

While he did not provide specific details about the alleged incidents, he insisted that the US would not hesitate to retaliate if Iran continued what he described as aggressive behaviour.

Trump also questioned Iran's sincerity in diplomatic negotiations, alleging that Iranian officials privately agreed to proposals during talks but later denied those discussions in public.

'They'll agree on everything, then walk out and say we never even talked,' he said, adding that Iranian leaders were 'behaving very badly.'

In one of his strongest remarks yet, Trump described Iran's leadership as 'cuckoo' and said the country had acted as 'the bully of the Middle East' for nearly five decades.

He maintained that Washington's primary objective remained preventing Iran from acquiring a nuclear weapon.

'They can't have a nuclear weapon. That's what I'm there for,' Trump said.

The US President further suggested that American forces could target additional Iranian naval assets and even disrupt critical infrastructure such as electricity and water facilities.

However, he later appeared to soften his stance, saying he hoped such measures would not become necessary.

Trump's comments come amid renewed military tensions in the Gulf following a series of strikes and counter-strikes involving US and Iranian forces.

The latest escalation has raised concerns over the possibility of a broader regional conflict, with global markets closely monitoring developments due to fears of disruptions to oil supplies and international shipping routes.

Iran has not immediately responded to Trump's latest warning, while the international community continues to urge restraint as fears of further military escalation grow.