ERBIL, Iraq—Populist cleric Moqtada al-Sadr signaled he is willing to form coalition with Iraq’s U.S.-backed prime minister that could soothe American concerns following the country’s surprising national parliamentary elections.
Mr. Sadr’s alliance of Shiite Islamists and communists unexpectedly captured the most parliamentary seats over the weekend, voting counts in the provinces of Kirkuk and Dohuk confirmed Tuesday evening. The cleric’s victory upended both American and Iranian calculations, as U.S.-aligned Prime Minister...