Iran's supreme leader Ayatollah Ali Khamenei said Wednesday that if the United States attacked Iran, US interests around the world would be harmed "double-fold", state-run Tehran television reported. "The Americans should know that if they invade Iran, their interests around the world would be harmed. Iran will respond double-fold to any attack," the television quoted Khamenei as saying. Speaking to laborers on the occasion of the International Laborers Day, Khamenei said US officials have been using threatening language for the past 27 years but the Iranian nation and officials would not care about the threats. "The Iranian nation and its officials are peace-seekers and the Islamic republic would not invade anybody," Khamenei said.