PARIS Britain, France and Germany have told the United Nations they are ready to reimpose U.N.-mandated sanctions on Iran over its nuclear programme if no diplomatic solution is found by the end of August, according to a joint letter obtained by AFP. The letter to U.N. Secretary-General Antonio Guterres and the U.N. Security Council says the three European powers are "committed to use all diplomatic tools at our disposal to ensure Iran does not develop a nuclear weapon" unless Tehran meets the