Donald Trump calls it "The worst deal ever". The question is why is he so hell-bent on decertifying a 2015 Iran nuclear agreement when even his own cabinet seems to support it? The move is consistent with the US president's bid to unwind any and all of the policies of his predecessor and on the day when Washington's announced it's pulling out of UNESCO for being too anti-Israel, how far will he go? Few expect the US to walk away from the deal but Trump could stiffen sanctions. Produced by Yann PUSZTAI, Alessandro XENOS, Christopher DAVIS.