Iran's President Hassan Rouhani hopes to bring his country out of diplomatic isolation - but despite his new tone and the promise of increased flexibility on Tehran's nuclear program, some critics warn the West is falling into a clever trap.
ITV News Washington Correspondent Robert Moore reports.
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After a mild start temperatures should pick up, with the south of England seeing highs of 26C.
In Edinburgh tonight you can hear it and feel it. The buzz, the banter of the day and the thrilling sense something big is coming tomorrow.
There is nervousness, anxiety and on the streets of Edinburgh fuelled by an atmosphere unlike anything seen before in recent UK politics.