Carter noted recent progress by Iraqi forces in retaking Ramadi, including the retaking of the Anbar Operations Center on the northern bank of the Euphrates River across from Ramadi’s city center.
"This is an important step, but there is still tough fighting ahead," Carter said.
"The United States is prepared to assist the Iraqi Army with additional unique capabilities to help them finish the job, including attack helicopters and accompanying advisers, if requested by Prime Minister Abadi," Carter said.
"I mention all this because it represents how we’ve adapted in the way we support our Iraqi partners. And it shows that training, advising and assisting is the right approach. We will do more of what works going forward," he added.
American Apache helicopters have been in Iraq since last summer but only in a force-protection capacity, though last fall Apache helicopters assisted Iraqi ground troops fighting west of Baghdad.
In July, Iraqi security forces began a military operation to retake Ramadi which had been seized by ISIS earlier this year.
Since then, American military officials have grown frustrated by the slow pace of the Iraqi operation as Iraqi troops faced a tougher than expected ISIS defenses. About 10,000 Iraqi troops have encircled the center portion of the city where it is believed hundreds of ISIS fighters remain.
The two scenarios outlined by Carter could place American troops closer to combat situations.
Currently, American advisers have been assisting the Iraqi assault on Ramadi from a higher-level headquarters. U.S. officials have said that under the new proposal, American advisers would work with Iraqi forces at the brigade headquarters level where they would be closer to the field of battle.
Though Apache helicopters can fire missiles from a distance, American pilots could be at risk from ground fire when engaged in close combat situations, as happened during the previous U.S. military presence in Iraq.
Senators emphasized that the recent San Bernardino attack should focus the U.S. military’s attention on retaking Raqqa, ISIS's de facto capital in Syria.
"I think it is pretty obvious to all that as long as they have a caliphate base, than they are able to orchestrate attacks such as they have successfully achieved in the last several weeks," said Sen. John McCain, R-Arizona, pointing to Ankara, the Russian airliner, southern Beirut, Paris and San Bernardino.
Carter noted that there is no current timeline for retaking Raqqa in Syria or Mosul in Iraq. And any push towards the city would likely involve the untested Sunni Arab force known as the Syrian Arab Coalition. Syrian Kurdish forces have retaken ISIS territory in northern Syria, but they have no interest in retaking Raqqa, a majority Arab city.
Showing the bipartisan concerns about Raqqa, Sen. Joe Donnelly, D-Indiana, pressed Carter that the need to retake Raqqa was about preventing a terror attack on U.S. soil.
“It is strongly believed by me and many others that as long as Raqqa is held and other areas are held, it dramatically increases the chance of another attack in our country,” Donnelly said. “When we ask when are we going to get to Raqqa and move them out, it's not because we're trying to find the date. It's because it's extraordinarily dangerous to the citizens of this country that they're there.”