BAGHDAD — The surprisingly strong showing of a ticket backed by maverick cleric Moqtada al-Sadr in Iraqi elections over the weekend will force U.S. officials to recalculate how best to proceed in the region at an especially sensitive moment.Sadr is a ferocious critic of American policies in the Middle East, and his unexpected electoral haul immediately calls into question the continuing presence of U.S. troops in Iraq. But his spokesman said Sadr supports honoring commitments between Iraq and the United States concerning the training of Iraq’s security forces and weapons purchases as long as they serve Iraq’s interests and there "is no interference on the sovereignty of Iraq."Sadr’s ticket won the most seats in Iraq’s parliamentary election, according to results from all 18 provinces released Monday, placing him in the best position to select the next prime minister and set the course for how the nation emerges from a costly war against the Islamic State.His ascendancy comes at the expense of incumbent Prime Minister Haider al-Abadi, the preferred candidate of the United States, who came in third.The Shiite cleric first gained international notice as a young militia leader who fought U.S. troops after the 2003 invasion.But Sadr has grown increasingly pragmatic over the years and formed a cross-sectarian electoral alliance emphasizing Iraqi nationalism over loyalty to Iranian clerics and American military and political backing. He has also broken ranks with Iraq’s Shiite establishment by denouncing Iran’s involvement in Syria’s civil war and its bid for expanded influence in Iraq."He’s the only politician with a clear vision for Iraq," said a Western diplomat who spoke on the condition of anonymity to give a frank assessment of Sadr. "Iraq first, eradicate corruption and a technocratic government."Tensions in the region have mounted — in particular between the United States and Iran — partly because of President Donald Trump’s decision last week to withdraw from the nuclear deal with Tehran.Sadr surprised allies and opponents alike with his strong showing across the majority of Iraqi provinces, where voters responded to his message of fighting corruption and reforming Iraq’s patronage-heavy political system.