Washington DC - President Donald Trump claimed a "new" leader in Iran had requested a ceasefire, but vowed to continue blasting the country "back to the Stone Ages" until the critical Strait of Hormuz shipping lane is reopened.

Trump, who is due to make a televised address later on Wednesday, did not name the "new regime president" who supposedly called for a truce, but said he was "much less radicalized and far more intelligent than his predecessors."

An Iran foreign ministry spokesperson called Trump's comments "false and baseless."

It is unclear with whom the US is claiming to have been negotiating, since many of Tehran's ruling figures have been assassinated and the current leadership is adamant it will only end the war on its terms.

In the face of ongoing military strikes by the US and Israel, Iran has tightened its grip on the Strait of Hormuz, sending global oil and gas prices skyrocketing, and dealing serious damage to US military assets in the region.

Trump has veered wildly between suggestions that he was looking to wind down the war and threats of apocalyptic destruction. That same pattern was evident in Wednesday's post, which ended with a boast that the US would be "blasting Iran into oblivion or, as they say, back to the Stone Ages!!!"

The conflict has strained trans-Atlantic tensions, with the US president frequently lambasting allies over their reluctance to being drawn into the fighting.