President Barack Obama has approved sending up to 1,500 more troops to Iraq, roughly doubling the number of U.S. forces on the ground to advise and retrain Iraqis in their battle against the militant group Islamic State, U.S. officials said on Friday.

Obama's decision greatly expands the scope of the U.S. campaign and the geographic distribution of American forces, some of whom will head into Iraq's fiercely contested western Anbar province for the first time to act as advisers.

It also raises the stakes in Obama's first interactions with Congress after his Democratic Party was thumped by Republicans in midterm elections Tuesday. The White House said it would ask Congress for $1.6 billion for a new "Iraq Train and Equip Fund."