Iran's supreme leader Ayatollah Ali Khamenei lashed out Sunday at the US and Britain, labelling them Tehran's main “enemies” and warning they will fail to isolate Iran over its nuclear issue, a report said. “Americans are at the head of the list of enemies and the British are the most awful of them,” state television reported Khamenei as saying in an address to thousands of people to mark a major Shiite ceremony. “Americans, Zionists and other oppressive powers tried to isolate Iran for the past 30 years, but they failed and with God's help they will also fail in the future,” Khamenei said in reaction to sustained Western threats to isolate Iran over its controverisal atomic program. “We ask them to stop lying and as we have said in the past the Iranian nation is pursuing nuclear technology and if we do not achieve it today, then tomorrow when the world economy is driven by nuclear power we will be late,” the cleric said, reasserting that Iran's nuclear intent is entirely peaceful. Meanwhile, Iranian authorities have slowed Internet connections to a crawl or choked them off completely before expected student protests Monday to deny the opposition a vital means of communication. In another familiar tactic before such rallies, authorities have ordered journalists working for foreign media organizations not to leave their offices to cover the demonstrations.