The United States will send up to 450 more troops to Iraq to boost the training of local forces, the White House says.
The move is a response to recent setbacks at the hands of the Islamic State and Baghdad's appeals for more help.
Under the plan, the number of US training sites in Iraq would increase from four to five, enabling a larger number of Iraqis to join the fight against the Islamic militant group.
Most of the fighters would be Sunni tribal volunteers.
The White House said President Barack Obama made the decision at the request of Iraqi Prime Minister Haider al-Abadi and based on advice from Pentagon leaders.
Mr Obama continues to resist demands for combat troops or for more US soldiers on the ground to call in air strikes.