The United States will deploy special operations forces to fight Islamic State jihadists in Iraq, with the ability to conduct raids over the border in Syria, Defense Secretary Ashton Carter said Tuesday.

Speaking to the House Armed Services Committee, the Pentagon chief said a "specialized expeditionary targeting force" would be deployed to help Iraqi and Kurdish Peshmerga forces battle the IS group. He did not say how many troops would be involved.

The special forces will also be able to intervene in neighboring northern Syria, where Washington previously announced it is sending about 50 special operations troops in a non-combat role.

"These special operators will over time be able to conduct raids, free hostages, gather intelligence, and capture ISIL leaders," he said.

"This force will also be in a position to conduct unilateral operations into Syria."

President Barack Obama has said the United States would not send large-scale, "boots on the ground" deployments of American troops to fight IS jihadists, and instead would intensify its air campaign against the group.

In late October, Obama authorized sending about 50 special operations forces to Syria in a non-combatant, advisory role to help coordinate local ground troops and anti-IS coalition efforts.

This marked the first official deployment of US troops on the ground in Syria since an international coalition formed last year to counter the jihadist group.

Carter said the Pentagon is "prepared to expand" the role of these troops in Syria.

"American special operators bring a unique suite of capabilities that make them force multipliers," Carter said.

"Where we find further opportunity to leverage such capability, we are prepared to expand it."

US lawmakers regularly haul senior officials into Congress to testify about the progress of the US-led effort to counter IS jihadists in Iraq and Syria.

The United States has been leading a coalition fighting IS in both countries since August last year and, though there are about 65 nations in the coalition, American warplanes and drones are doing the lion's share of the work.

Despite more than a year of daily plane and drone strikes against the IS group, the United States is still struggling to defeat the jihadists.

Carter was joined by his top commanding officer General Joe Dunford. Asked whether the IS group had been "contained," Dunford said: "We have not contained ISIL."

Speaking more than two weeks after terror attacks in Paris left 130 dead, Carter called on international powers to ramp up efforts to defeat IS.

"The international community -- including our allies and partners -- has to step up before another attack like Paris," he said.

"The more contributions we receive from other nations, the greater combat power we can achieve using our own force."

His comments come as the British parliament prepares to debate whether the Royal Air Force should start bombing in Syria.