ISTANBUL/MOSCOW (Reuters) -Iran's supreme leader sent his foreign minister to Moscow on Monday to ask President Vladimir Putin for more help from Russia after the biggest U.S. military action against the Islamic Republic since the 1979 revolution over the weekend. U.S. President Donald Trump and Israel have publicly speculated about killing Supreme Leader Ayatollah Ali Khamenei and about regime change, a step Russia fears could further destabilize the Middle East.