Donald Trump was pulled back from striking Iran by last-minute diplomatic efforts from Persian Gulf states, it is understood.

Saudi Arabia, Qatar and Oman led urgent talks with Washington aimed at persuading the US president to delay military action and allow Tehran to demonstrate “good intentions”.

Mr Trump had told Iranian protesters that help was “on the way” and threatened the regime with strikes if more people died.

But later on Wednesday he appeared to step back from imminent action, saying he had been assured that “the killing in Iran is stopping”.

Shortly beforehand, Tehran cancelled the planned execution of a protester, while the foreign minister said there was “no plan” to carry out hangings.

A senior Saudi official told AFP that the Gulf states had mounted a “long, frantic, last-minute diplomatic effort” to convince Mr Trump to give Iran a chance, warning of “grave blowback in the region”.

“It was a sleepless night to defuse more bombs in the region,” the official said, adding that talks were continuing “to consolidate the gained trust and the current good spirit”.

Other countries, including Turkey and Egypt, also urged Mr Trump to show restraint, warning of the potential impact on Iran’s neighbours and on global oil and gas prices, sources told the Financial Times.