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Defense Secretary Ashton Carter said Tuesday that the U.S. will begin “direct action on the ground” against ISIS forces in Iraq and Syria, aiming to intensify pressure on the militants as progress against them remains elusive.

“We won't hold back from supporting capable partners in opportunistic attacks against ISIL, or conducting such missions directly whether by strikes from the air or direct action on the ground," Carter said in testimony before the Senate Armed Services committee, using an alternative name for the militant group.

Carter pointed to last week’s rescue operation with Kurdish forces in northern Iraq to free hostages held by ISIS.

Related: Master Sgt. Joshua Wheeler, U.S. Commando Killed in ISIS Raid, Ran to Gunfight

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Carter and Pentagon officials initially refused to characterize the rescue operation as U.S. boots on the ground. However, Carter said last week that the military expects "more raids of this kind" and that the rescue mission "represents a continuation of our advise and assist mission."

This may mean some American soldiers "will be in harm's way, no question about it," Carter said last week.

After months of denying that U.S. troops would be in any combat role in Iraq, Carter late last week in a response to a question posed by NBC News, also acknowledged that the situation U.S. soldiers found themselves in during the raid in Hawija was combat.

"This is combat and things are complicated," Carter said.

During Tuesday's Senate hearing, Carter said Wheeler "was killed in combat."

White House deputy press secretary Eric Schultz on Tuesday said the administration has "no intention of long term ground combat". He added that U.S. forces will continue to robustly train, advise and assist.

A feisty Sen. Lindsey Graham, R-South Carolina, said on Tuesday in the Senate Armed Services committee hearing that the U.S. effort in Syria is a "half-assed strategy at best," and said that the U.S. is not doing a "damn thing" to bring down Syrian President Bashar Assad's regime.

Carter on Tuesday pushed back against that notion.

Gen. Joseph Dunford, chairman of the Joint Chiefs of Staff, acknowledged that the "balance of forces" has tilted in Assad's favor.