In Shift, U.S. Will Send 450 Advisers to Help Iraq Fight ISIS

Mr. Obama will also speed up the delivery of weapons and equipment to Iraqi forces, including pesh merga and tribal fighters who are under Iraqi command.

The new plan follows months of behind-the-scenes debate about how prominently plans to retake Mosul, another Iraqi city that fell to the Islamic State last year, should figure in the early phase of the military campaign against the group.

The Obama administration took pains to assert that the steps did not constitute a change in strategy.

“This decision does not represent a change in mission, but rather adds another location for D.O.D. to conduct similar activities in more areas in Iraq,” the Department of Defense said in a statement. “This effort is in keeping with our overarching strategy to work with partners on the ground to degrade and ultimately defeat ISIL.”

It said the new location would bring American troop levels in Iraq up to 3,550.

The fall of Ramadi last month effectively settled the administration debate, at least for the time being. American officials said Ramadi was now expected to become the focus of a lengthy campaign to regain Mosul at a later stage, possibly not until 2016.

The additional American troops will arrive as early as this summer, a United States official said, and will focus on training Sunni fighters with the Iraqi Army. The official called the coming announcement “an adjustment to try to get the right training to the right folks.”

But the Obama administration hopes that the outreach will reduce the Iraqi military’s reliance on Shiite militias to take back territory from the Islamic State. “The Sunnis want to be part of the fight,” the official said, speaking on the condition of anonymity. “This will help empower them, creating more recruits and more units to fight ISIL,” he added, using another acronym for the Islamic State.

The United States is not the only country that is expanding its effort.

Britain’s prime minister, David Cameron, said this week that his country would send up to 125 additional troops to train Iraqi forces, including in how to clear improvised bombs.

Italy is also expected to play an important role in training the Iraqi police.

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