Known as Persia until 1935, Iran was one of the greatest empires of the ancient world. Iran became a unique Islamic republic in 1979, when the monarchy was overthrown and religious clerics assumed political control under supreme leader Ayatollah Khomeini. Since then, Iran has experienced an eight-year (1980-1988) war with Iraq, internal political struggles and unrest, economic disorder, and severe human rights violations. Ayatollah Khomeini died in 1989, and Ayatollah Ali Khamenei was appointed for life as the supreme leader. Since 1979, Iran has been led by conservatives who have kept reformers at bay. The elections of June 2005 dealt a blow to the reformists when Mahmoud Ahmadinejad, Tehran's ultra-conservative mayor, became president. Ahmadinejad's controversial re-election in June 2009 has further widened the rift between conservatives and reformists. Iran remains subject to United States, United Nations, and European Union economic sanctions and export controls because of its continued involvement in terrorism and its nuclear weapons ambitions. The United Nations Security Council has passed a number of resolutions calling for Iran to suspend its uranium enrichment and reprocessing activities. Iran has an abundance of energy resources. It is OPEC’s second largest oil producer and holds about 10 percent of the world’s proven oil reserves. It also has the world’s second largest natural gas reserves (after Russia). However, heavy government control, corruption and inefficiency have weighed down the economy.