Iraq’s Kurds have been enthusiastic U.S. allies since before the 2003 invasion. But as the Kurds have expanded their control over their oil-rich territory—and as they reassert claims to the contested city of Kirkuk ahead of a constitutionally mandated referendum—tensions are mounting with the central government of Prime Minister Nuri al-Maliki and with Arabs and other ethnic groups. Last week, Massoud Barzani was reelected president of the Kurdistan Regional Government despite a strong opposition showing. Days later, he sat down with NEWSWEEK’s Larry Kaplow in his mountain complex high above the Kurdish city of Irbil. Excerpts: