Donald Trump has said he will be "indirectly" involved in the talks between Iran and the United States which are due to begin in Geneva later on Tuesday.

Axar.az informs, citing BBC, speaking to reporters aboard Air Force One, the US president added that he believed Iran wanted to make a deal over its nuclear programme.

The second round of talks in Switzerland follows repeated military threats against Iran over the country's deadly crackdown on anti-government protests and the ongoing dispute over its nuclear programme.

On Monday the foreign ministry in Tehran said it believed that the US position on the nuclear issue had moved towards "a more realistic one".

Iran says Tuesday's meeting, mediated by Oman, will focus on its nuclear programme and the potential lifting of economic sanctions imposed by the US. Washington has previously indicated it wants to discuss other issues as well, such as Iran's missile stockpile.

Framing the talks as "very important", Trump suggested Tehran was motivated this time to negotiate.

"I don't think they want the consequences of not making a deal," Trump said, adding that Iran learned the consequences of a tough posture in talks last summer when the US bombed Iranian nuclear sites.

"We could have had a deal instead of sending the B-2s in to knock out their nuclear potential. And we had to send the B-2s," Trump said, referring to the stealth bombers that carried out the bombings. "I hope they're going to be more reasonable."