US President Barack Obama has approved the deployment of up to 450 extra military personnel to Iraq to train and advise forces fighting Islamic State militants.
The US troops will be based in Anbar province, where IS has made major gains, but will not have a combat role.
The move is aimed at enabling more Iraqis - mostly Sunni tribal volunteers - to integrate into the Iraq army and reclaim territory from Islamic State.
President Obama made the decision following a request from Iraqi Prime Minister Haider Al-Abadi, a White House statement said.
"These new advisers will work to build capacity of Iraqi forces, including local tribal fighters, to improve their ability to plan, lead, and conduct operations" against IS in Anbar, the statement added.
The added personnel would bring the total of US military personnel, including trainers and advisers, in Iraq to 3,550 troops. The UK is sending an extra 125 troops to 275.
The troops will be deployed to the Taqaddum military base in Anbar province. IS seized Ramadi - the capital of Anbar - in May.
Later that month pro-government forces in Iraq formally launched an operation to drive Islamic State out of the province.
US officials believe a major factor in the fall of Ramadi was a lack of training of Iraqi forces.
However, former Iraqi national security adviser Mowaffak al-Rubaie told the BBC the new plans were not enough.
"This is too little too late. I call for the American administration to get their act together." he added.
"They don't have any unified strategy. We don't understand their policy in Iraq and in Syria, in the region. They are giving conflicting signs."