Iran and the United States concluded a fifth round of high-stakes nuclear talks in Rome on Friday amid growing skepticism in Tehran about the chances of a deal as Washington hardens its position.

Iranian and U.S. negotiators resumed talks on Friday in Rome to resolve a decades-long dispute over Iran's nuclear ambitions, Iranian media reported, despite Tehran warning that clinching a new deal might be insurmountable amid mutually exclusive demands.

Trump in his first term in 2018 ditched a 2015 nuclear pact between major powers and Iran. Since returning to office this year, he has restored a "maximum pressure" campaign on Tehran and reimposed sweeping US sanctions that continue to hobble the Iranian economy.