By Ned Parker BAGHDAD, June 23 (Reuters) - In eight years in power, Iraq's prime minister Nuri al-Maliki has never faced such a threat. Foreign sponsors in Washington and Tehran are wary or worse. Yet the virtuoso player of Iraq's political game shows ** sign of surrendering any time soon. His opponents say Maliki is responsible for the vehemence of the insurgency because of policies that alienated Sunnis, pushing tribes to back a revolt by the Islamic State in Iraq and the Levant, which seized the main **rthern city Mosul on June 10 and has since marched virtually u**pposed towards Baghdad.