Iran pledged on Monday to retaliate "ferociously" against any U.S. attack and reiterated its warning of a potential regional conflict in response to President Donald Trump's latest threat of strikes.

The bellicose rhetoric from both Tehran and Washington came as the foes prepared for indirect talks in Geneva on a potential deal regarding Iran's nuclear programme, after a U.S. official confirmed discussions would resume on Thursday, The Caspian Post reports, citing foreign media.

Even as Iran faces U.S. pressure backed by a build-up of military force in the Middle East, university students have started the new semester with anti-government protests, reviving slogans from nationwide demonstrations that peaked in January and were met with a deadly crackdown.

Last week, Trump said he was weighing a limited strike if Iran did not cut a deal, but Tehran's foreign ministry said Monday that any strike, even limited, "would be regarded as an act of aggression".

"And any state would react to an act of aggression... ferociously, so that's what we would do," ministry spokesman Esmaeil Baqaei said.

Iran has said it will be ready to deliver a draft proposal for an agreement on its nuclear programme to mediators in the coming days. Trump said on Thursday that Tehran had at most 15 days to make a deal.