President Barack Obama on Wednesday ordered the deployment of up to 450 more U.S. troops and the establishment of a new training base in Iraq's Anbar province to help rebuild fragile Iraqi forces in preparation for a battle to retake territory lost to Islamic State.

The plan to expand the 3,100-strong U.S. contingent of trainers and advisers in Iraq marks an adjustment in strategy for Obama, who has faced mounting pressure to do more to blunt the momentum of Islamic State insurgents.

But with Obama sticking to his refusal to send troops into combat or to the front lines, it is unlikely to silence critics who say the limited U.S. military role in the conflict is not enough to turn the tide of battle.