Defense Secretary Ash Carter's blunt assessment that Iraqi forces lack the "will to fight" is undermining a central premise of President Barack Obama's strategy for defeating the Islamic State group. That is the assumption that Iraq's military can effectively handle ground operations so American forces don't have to.

Carter's comments in a weekend interview reflect deep concern within some quarters of the administration about the capabilities of Iraq's security forces. Despite outnumbering Islamic State forces and being well-trained and equipped after years of American assistance, the military suffered a major defeat this month in the city of Ramadi.

Some officials also question whether Iraq's forces can overcome the same sectarian divisions between Sunnis and the Shiite-dominated government that have given the Islamic State space to thrive.