DOHA, Qatar (AP) — As U.S. Secretary of State Rex Tillerson visits the Middle East this weekend, he'll hope to achieve something that has eluded top American diplomats for a generation: sealing a new alliance between Saudi Arabia and Iraq that would shut the doors of the Arab world to neighboring Iran. While the United States strives to heal the rift between the Gulf Arab states and Qatar, and resolve civil wars in Yemen and Syria, Tillerson is the Trump administration's point man on an even more ambitious and perhaps even less likely geopolitical gambit. U.S.