Defense Secretary Ash Carter said Tuesday the U.S. military will deploy a specialized expeditionary targeting force to Iraq to launch unilateral raids and "put even more pressure" on ISIS.

U.S. special operation forces will conduct operations in Iraq “at the invitation of the Iraqi government” and be in position “to conduct unilateral operations into Syria,” Carter said.

"We're at war. We're using the might of the finest fighting force the world has ever known," Carter told the House Armed Services Committee. "Tens of thousands of U.S. personnel are operating in the broader Middle East region, and more are on the way."

While Carter did not divulge much about the special ops forces that will be battling ISIS, DOD officials have told NBC News that the expeditionary targeting force would be permanently based in Iraq. According to the officials, the force would be comprised of 100 to 150 special operations forces that would conduct ground combat raids against ISIS targets in both Iraq and Syria.

The objective would be to gather intelligence, free hostages or prisoners and kill or capture ISIS leaders. In between combat operations the American commandos would assist and could accompany Iraqi and Kurdish forces on their military operations against ISIS targets. No timetable was given on when the special operations forces will begin to arrive in Iraq.

The U.S. will consult with the Iraqi government, but there may be times when they don't give Baghdad advance notice that an operation is underway. One official also pointed out that when talking about coordination with Iraqi forces “that also includes the Kurds.”

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The officials stressed the operations would not involve “large numbers of forces” and be limited to smaller special operations expeditionary units.

Whatever the number, one senior official told NBC News, “this cracks open the door” for U.S. combat operations in Iraq and Syria.

The special ops missions would be along the lines of the October raid in northern Iraqi where they helped Kurdish fighters free 70 prisoners being held by ISIS, senior defense officials interviewed by NBC News said. One U.S. Special Operations commando was killed in that raid.

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At the time, Carter openly acknowledged that the ground forces had been involved in combat operations and there would be more such raids.

The 50 special operations forces that the president and Pentagon previously announced were headed for northeastern Syria, will not be directly involved in ground combat operations. Their job is to assist and advise mostly Kurdish forces in their combat ops against ISIS targets in Syria and will be “semi-permanently” located at a Kurdish military operations center at what is presumed to be a safe distance from any ground combat with Syria.

Related: U.S. to Deploy Special Operations Forces in Syria: Officials

Defense officials said the number of special operations forces and where they will be deployed in Iraq has yet to be determined.

Calling the recent bloody terror attack on Paris an "assault on the civilization we defend," Carter vowed ISIS would be destroyed.

"We are acting to defeat ISIL at its core," said Carter, using the government's acronym for ISIS.

Carter discussed strategy and noted that U.S.-backed Kurdish forces had recently retaken the strategic town of Sinjar and cut off ISIS's "main line of communication" between Raqqa, Syria and Mosul, Iraq, which are the two biggest cities still under their control.

Before Carter went before lawmakers, Obama in Paris defended his administration's strategy against ISIS.

President Obama was harshly criticized for claiming that ISIS was "contained" shortly before the deadly Paris terrorist attacks.

On Wednesday, Sen. John McCain, R-Ariz., chairman of that chamber's Armed Services committee, characterized the administration's approach as "incremental".

"We don't have a strategy. What we're doing, what this administration is doing, is incrementally adding capabilities and in reaction to ISIS activities. Rather than taking the initiative and developing the overall strategy," McCain told reporters at a Christian Science Monitor breakfast.

At Tuesday's House hearing, Gen. Joseph Dunford, the chairman of the Joint Chiefs of Staff, said "We have not contained" ISIS.

The Obama administration has faced criticism for its ISIS strategy, especially from Republican lawmakers who have called for a more hawkish approach to crushing the murderous militant group.

Skeptical Republicans pushed Carter to respond to allegations they are being given a “rosy picture” of how well the fight is going against ISIS.

“The territory under ISIL’s control has shrunk, that is a fact,” Carter said, noting that Kurds are now controlling those areas in Iraq and Syria. “That’s not a declaration of victory.”

Pressed to say if they were winning, Carter said, “We’re going to win.”