US Defence Secretary Ashton Carter has said the rout of Iraqi forces at the city of Ramadi showed they lacked the will to fight against Islamic State.
Mr Carter told CNN's State of the Union the Iraqis "vastly outnumbered" the IS forces but chose to withdraw.
The head of Iraq's defence and security committee said the comments were "unrealistic and baseless".
The Iraqi government has now deployed Shia militias to the area to try to halt the advance of IS.
On Saturday, the militiamen retook Husayba, east of Ramadi, the capital of Anbar province, with heavy fighting continuing in the area on Sunday.