Iran's supreme leader Ayatollah Ali Khamenei said Tuesday Tehran will reject any dialogue if its result is fixed by Washington, raising the possibility a mooted nuclear fuel deal may be derailed. "We do not want any negotiation, the result of which is pre-determined by the United States," Khamenei said in a speech to students on the eve of Wednesday's 30th anniversary of the US embassy seizure by radical Islamist students in Tehran.