WASHINGTON -- The U.S. military will deploy a new special operations force to Iraq to step up the fight against Islamic State militants unleashing violence in Iraq and Syria and determined to hold territory they have seized across the Middle East, Defense Secretary Ash Carter told Congress on Tuesday.

Carter, who testified alongside Gen. Joseph Dunford, chairman of the Joint Chiefs of Staff, faced skeptical lawmakers who argued the U.S. needs to be more forceful in countering the threat from IS, credited with attacks in Paris and Beirut and the downing of a Russian airliner.

Carter told the House Armed Services Committee that over time, the special operations force will be able to conduct raids, free hostages, gather intelligence and capture IS leaders. Carter said that will improve intelligence and generate more targets for attacks.

There are about 3,300 U.S. troops in Iraq, and President Barack Obama previously had announced he was sending fewer than 50 special operations forces to Syria.

There has been a growing call from some Republicans for more U.S. boots on the ground and a divide among war-weary Americans about the prospect of greater military involvement.

Carter said the number in the new expeditionary force will be "larger" than 50. He said it will be a "standing" force, meaning it will be stationed in Iraq.