With a conventional military and weapons of mass destruction (WMD) threat from Saddam Hussein's regime removed, Iran seeks to ensure that Iraq can never again become a threat to Iran, either with or without U.S. forces present in Iraq. By supporting armed Shiite factions, Iran's influence in Iraq has at times hindered U.S. efforts to stabilize Iraq, and has heightened the U.S. threat perception of Iran generally. However, Iran faces difficult choices in Iraq now that its protege Shiite factions, formerly united, are competing and often fighting each other.