The United States and Iran are due to hold their second round of nuclear talks on Saturday, as what both sides are looking for in a deal begins to take shape.

Iran and the United States will hold a new round of nuclear talks in Rome on Saturday to resolve their decades-long standoff over Tehran's atomic aims, under the shadow of President Donald Trump's threat to unleash military action if diplomacy fails.

As far as biographies go, the two men in charge of the delicate negotiations between Iran and the United States over Tehran’s rapidly advancing nuclear program couldn’t be more different.