President Barack Obama, trying to reassure war-weary Americans, vowed on Wednesday the United States will not fight another ground war in Iraq but his spokesman said some military advisers could end up in front-line positions against Islamic State.

Obama, who has spent much of his presidency distancing himself from the Iraq war, stressed that airstrikes would be the central U.S. contribution to the fight against Islamic State in Iraq and Syria, along with coordinating a coalition that he said now includes more than 40 countries.

"I want to be clear. The American forces that have been deployed to Iraq do not and will not have a combat mission," Obama said in a speech at MacDill Air Force Base in Tampa.