WASHINGTON — The Pentagon will expand its Special Operations force in Iraq as part of a ramped-up war effort against the Islamic State in Iraq and Syria, Defense Secretary Ashton B. Carter told a House hearing on Tuesday.

Mr. Carter said that a specialized expeditionary American military force would be able to target Islamic State militants in Iraq and make targeted raids into Syria. “These special operators will over time be able to conduct raids, free hostages, gather intelligence and capture ISIL leaders,” Mr. Carter said, using an acronym for the Islamic State.

Mr. Carter did not say precisely how many new forces would be added but said they would be more than 50. He also did not say where exactly they would be based in Iraq. A Defense Department official said on Tuesday that these would be new troops and not troops reassigned from other parts of Iraq.

President Obama has already authorized the deployment up to 50 special operators in Syria to help organize Arab and Kurdish fighters there.