WASHINGTON -- U.S. Defense Secretary Ash Carter says the United States will expand its involvement in the fight against Islamic State (IS) militants in Iraq, deploying an "expeditionary targeting force" to help local forces and conduct more raids both in Iraq and neighboring Syria.
The comments by Carter on December 1 come amid growing pressure from Congress to do more to curtail the increasingly ambitious attacks by the radical group, which has claimed responsibility for last month's Paris attacks and holds vast areas of Syria and Iraq.
Carter and the top U.S. military commander, General Joseph Dunford, faced tough questions from members of the House of Representatives' Armed Service Committee as they gave an optimistic view of the fight against IS forces.
About 3,500 U.S. troops are in Iraq and recently helped Iraqi Kurdish forces and other units take back the strategic northern city of Sinjar. In Syria, the U.S. administration is deploying around 50 special operations forces to work alongside Kurdish and Syrian Arab fighters to battle the militants, mainly in the north.
The U.S. efforts in Iraq, while ostensibly backed by the government of Prime Minister Haidar al-Abadi, face pitfalls from powerful Shi'ite militias that are largely autonomous from government security forces but have also battled IS militants.
Several Shi'ite militia leaders, some allied with Iran, told Reuters that they would fight any expanded deployment of U.S. forces to Iraq.
Carter said U.S.-backed militias had taken the Syrian city of Al-Hawl last month, along with around 1,500 square kilometers of territory, and were beginning to move south toward the central city of Raqqa, an IS stronghold.
Carter did not provide specific numbers for the "expeditionary targeting force" but said it would be larger than the force that President Barack Obama announced would be heading back to Syria.
He said the expanded force's missions would include conducting raids, rescuing hostages, gathering intelligence, and trying to capture or kill IS leaders.
"This is an important capability because it takes advantage of what we're good at," he told the committee.
"We're good at intelligence. We're good at mobility. We're good at surprise. We have the long reach that no one else has. And it puts everybody on notice in Syria: You don't know at night who's going to be coming in the window. And that's the sensation that we want all of [the IS] leadership and followers to have," Carter said.
"This force will also be in a position to conduct unilateral operations into Syria," he added.
Carter said the United States was also expanding attacks on the militants' infrastructure and their sources of revenue, particularly from oil.
Dunford, who serves as chairman of the Joint Chiefs of Staff, told the committee that air strikes from the U.S.-led coalition have disrupted 43 percent of the group's revenue streams over the past month.
Officials have said oil smuggling has been a primary source of revenue for the group's efforts to build a theocratic state known as a caliphate, along with cement production and local taxes.
Carter also praised France for its expanded role in Syria, taken after the Paris terrorist attacks last month, and he called on other countries to do more, Turkey in particular. He noted that Turkish attacks had mainly targeted Kurdish militias, in particular the banned separatist group, the Kurdistan Workers Party.
"We need [Turkey] to do more within its own territory, so it controls its border, which it has not done effectively since ISIL first arose," he said, using an alternate acronym for the group.
"We would like them to operate more both in the air and on the ground," Carter said. "Most of the air operations are not directed at ISIL."
Dunford appeared to tamp down some calls by members of Congress and defense experts, who say that only by deploying a larger military force -- not air strikes alone -- can the extremist group be defeated.
IS militants "would love nothing more than to have a large presence of U.S. forces on the ground so they could have a call to jihad," he said.