Trump Calls for Keeping Troops in Iraq to Watch Iran, Possibly Upending ISIS Fight

President Trump plans to keep United States troops in Iraq to monitor and maintain pressure on neighboring Iran, committing to an American military presence in the region’s war zones even as he moves to withdraw forces from Syria and Afghanistan.

“I want to be able to watch Iran,” Mr. Trump said in an interview aired Sunday on CBS’s “Face the Nation.” “We’re going to keep watching and we’re going to keep seeing and if there’s trouble, if somebody is looking to do nuclear weapons or other things, we’re going to know it before they do.”

Mr. Trump’s comments come as the United States has quietly been negotiating with Iraq for weeks to allow perhaps hundreds of American commandos and support troops now operating in Syria to shift to bases in Iraq and strike the Islamic State from there. Military leaders are seeking to maintain pressure on the militant group as the president fundamentally reorders policy toward Syria and toward Afghanistan, where peace talks with the Taliban are underway.

But senior American officers and diplomats said Mr. Trump’s comments could undercut the delicate negotiations in Iraq by inflaming fears among the Iraqis that the moves would be a guise to check Iran, potentially straining ties with Baghdad and weakening the ability of the United States to respond to Islamic State remnants in Syria.