Washington DC - President Donald Trump on Monday warned Iran of the "consequences of not making a deal" ahead of talks between the US and the Islamic republic in Geneva.

"I'll be involved in those talks, indirectly," the US president told reporters aboard Air Force One en route to Washington.

"I don't think they want the consequences of not making a deal," Trump added.

The latest talks, scheduled Tuesday and mediated by Oman, follow repeated threats from Trump of military action against Tehran – first over Iran's response to anti-government protests, and then more recently over the country's nuclear program.

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The US and some European countries fear the program is aimed at making a bomb, which Tehran denies.

Washington has previously pushed for other topics to be discussed, including Iran's ballistic missiles and support for armed groups in the Middle East.

Iran's foreign ministry said earlier Monday that "the US position on the Iranian nuclear issue has moved towards a more realistic one."

A previous attempt at negotiations collapsed when Israel launched surprise strikes on Iran, beginning a 12-day war that Washington joined to bomb Iranian nuclear sites.