U.S. Defense Secretary Ash Carter on Sunday said Iraqi forces showed no will to fight against Islamic State of Iraq and Syria (ISIS) militants during the fall of Ramadi a week ago, and U.S. forces were trying to encourage them to engage more directly.

“The Iraqi forces just showed no will to fight,” Carter told CNN’s “State of the Union” program. “They vastly outnumbered the opposing force and yet they withdrew from the site.”

Carter said that for now, the United States was continuing to provide air strikes and supply Iraqi forces with training and equipment, but Washington was keeping a close watch on the situation.

“Air strikes are effective, but neither they nor anything we can do can substitute for the Iraqis’ will to fight. They’re the ones who have to beat ISIL and then keep them beat,” he said.

He said the U.S. military had not recommended any changes for now in the support Washington is giving to Iraq.

“If there comes a time when we need to change the kinds of support we’re giving to the Iraqi forces, we’ll make that recommendation,” Carter said, when asked about growing calls from Republican lawmakers for putting U.S. ground combat forces into Iraq.

Michele Flournoy, chief executive of the Center for a New American Security, told CNN that Washington needed to press the Iraqi government to provide more resources to the Sunni tribes in the western part of Iraq, who had a greater “political will to fight” than Iraqi forces.

Flournoy, a former undersecretary of defense for policy, welcomed Carter’s comments about doing more if needed.

“Now is that time, in my view,” she said.