Iran's Supreme Leader says US breaches show Trump's signature is 'worthless'

July 18 (Reuters) - Iran's Supreme Leader Mojtaba Khamenei said ​in a written statement ‌on Saturday that repeated U.S. breaches of a ​memorandum of understanding ​signed by the presidents ⁠of Iran and the ​United States had ​shown that President Donald Trump's signature was "utterly worthless and devoid ​of credibility."