United States President Donald Trump on Thursday expressed that he wanted “direct talks” with Tehran over a nuclear deal after he issued a stark warning of potential military action against Iran if it continues to advance its nuclear weapons programme.

Trump has set a two-month countdown for Iran to negotiate on its nuclear activities, which have long been a source of tension between Iran and Western nations.

Western countries, including the United States, have long accused Iran of pursuing a nuclear weapon, which Tehran has denied, insisting its enrichment activities were solely for peaceful purposes.

“I think it’s better if we have direct talks,” he told reporters onboard the presidential plane Air Force One. “I think it goes faster, and you understand the other side a lot better than if you go through intermediaries.”

Iran’s Foreign Minister Abbas Araghchi said last week that Tehran would not engage in direct talks with Washington “until there is a change in the other side’s approach towards the Islamic republic”.

Trump in his first term ripped up a 2015 nuclear deal negotiated by predecessor Barack Obama and reimposed crippling sanctions on Iran.

The deal, sealed between Tehran and world powers, had required Iran to limit its nuclear ambitions in exchange for sanctions relief.

“They wanted to use intermediaries. I don’t think that’s necessarily true anymore,” Trump said.

“I think they’re concerned, I think they feel vulnerable. I don’t want them to feel that way,” he added. “I think they want to meet.”

Trump said last month he had written to Iran’s supreme leader Ayatollah Ali Khamenei to call for nuclear negotiations and warn of possible military action if Tehran refused.

Trump gave the Iranians a two-month deadline to reach a new nuclear deal.

In response, Tehran has agreed only to indirect negotiations. It has ruled out any direct talks while under a US policy of “maximum pressure”, according to The Conversation.

Khamenei responded by saying that US threats “will get them nowhere” and warned of reciprocal measures “if they do anything malign” against Iran.

Last week, Trump said “there will be bombing” of Iran if it does not drop its efforts to develop nuclear weapons. In recent days, American B-2 bombers and warships have been deployed to the region in a show of force.