WASHINGTON — Congress members returning to Capitol Hill next week will face a debate over President Barack Obama’s new $5.6 billion plan to expand the U.S. mission in Iraq and send up to 1,500 more American troops to the war-torn nation.

Obama authorized the deployment of advisory teams and trainers to bolster struggling Iraqi forces across the country, including into Iraq’s western Anbar province where fighting with Islamic State militants has been fierce. His decision comes just three days after bruising midterm elections for his Democratic Party.

But the deployments hinge on whether Obama can get the funding approved in Congress’ lame-duck session, so that advisers can begin deploying to Iraq, particularly to Anbar where Sunni tribes have persistently requested help.

Obama’s plan could boost the total number of American troops in Iraq to 3,100. There are currently about 1,400 U.S. troops there, out of the 1,600 previously authorized.

The Iraqi government, members of Congress and others have called for troops in Anbar in western Iraq, where extremists have been slaughtering men, women and children.