President Barack Obama has approved sending up to 1,500 more troops to Iraq, roughly doubling the number of US forces on the ground.
The White House said it would also ask Congress for $1.6 billion for a new "Iraq Train and Equip Fund" and billions more for operations to battle IS.
Pentagon spokesman Rear Admiral John Kirby said the funds would need to be approved before the first additional forces head to Iraq, which could happen within weeks.
Kirby added: "(Iraqi forces are) going on the offence now. And what this is designed to do is to help them continue to be able to do that, to improve their capability and their competence on the battlefield."
He stressed no American troops would take on combat roles.
Around 1,400 US troops are currently on the ground but the new authorisation gives allows the US military to deploy up to 3,100.
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