“It’s a democratic process at a time when people, many people, doubted that Iraqis could take charge of themselves,” Mr. Mattis said on Tuesday.
As a young man, Mr. Sadr led a Shiite militia that targeted American troops in Iraq. He fled to Iran to study in Qom, a revered Shiite religious center, before returning to Iraq in 2011 as a cleric and strident Iraqi nationalist. Mr. Sadr is not expected to hold elected office in Iraq; rather, his power comes from his pulpit.
Given Iran’s outsize and yearslong influence in internal Iraqi politics, foreign policy experts said the Trump administration might have already made things more complicated for itself in Baghdad.
Mr. Trump’s decision last week to withdraw from the Iranian nuclear accord has frozen relations between Washington and Tehran after a thaw that, among other issues, had helped facilitate an indirect partnering against the Islamic State in Iraq.
Iran now “has no motivation for a leader in Iraq who would be positive toward the United States,” said Vali Nasr, the dean of the Johns Hopkins School of Advanced International Studies.
But Pentagon officials are betting that Iran also does not want to see a return of the Islamic State.
There is widespread agreement among Shiite political blocs, with whom Mr. Sadr would have to ally to form a government, to continue a program backed by international troops to train and equip Iraqi security forces. Trainers include American, Italian and Spanish advisers, with equipment paid for by the United States. And having NATO serve as the public representative for the American-led mission in Iraq could serve as a workaround for Mr. Sadr’s sensitivities, officials say.