Iraq could be asked to take any Iraqi citizens captured, but if there are Syrians or foreign fighters captured by the U.S. it's not clear what will happen to them. In May, U.S. Delta Force commandos captured a woman named Umm Sayyaf, wife of senior ISIS operative Abu Sayyaf. U.S. troops turned her over to the Iraqis.
This time, however, no decisions have been made on where people will be held -- or who will interrogate them -- especially if Syrian or European ISIS leaders are captured.
This is just one of the many issues to be decided after Defense Secretary Ash Carter testified on initials details of the force.
"These special operators will, over time, be able to conduct raids, free hostages, gather intelligence and capture ISIL leaders," he told Congress. "This force will also be in a position to conduct unilateral operations in Syria."
The troops who will go on raids will come from the often secretive Joint Special Operations Command (JSOC), based at Fort Bragg, North Carolina. JSOC for months has been already collecting intelligence on ISIS operatives and targeting them with drone attacks. This will put them closer to the front lines, allowing them to react faster officials say.
It's become especially vital because of ISIS's growing ability to operate in encrypted portions of cyberspace for U.S. troops to react as quickly as they can after getting intelligence tips.
So many details remain to be worked out however, officials say, it could be weeks before the troops arrive. They are expected to be based in Irbil, Iraq. Officials initially have said the total force, including helicopter support, could total 200. But the U.S. military spokesman in Baghdad, Col. Steve Warren, suggested it could total around 100.
The plan to send U.S. special operations forces into Iraq and Syria on anti-ISIS missions was approved by President Barack Obama last week in a White House meeting with only broad based details of the idea being laid out, according to a U.S. official familiar with the discussions.
The U.S. has agreed that any operations inside Iraq will be coordinated and conducted alongside Iraqi forces.
There are also concerns inside the Pentagon that Iranian backed militias inside Iraq and Syria could see the U.S. forces as intrusive and could start targeting them, the officials say.
The White House and State Department are underscoring that the Iraqi government is in agreement with the U.S. plan.
"The government in Iraq was of course fully briefed in advance of Secretary Carter's announcement," Kerry said at a news conference at the NATO headquarters in Brussels.
Kerry was answering a question about comments by Iraqi Prime Minister Haider al-Abadi saying that no foreign forces would be allowed to deploy without Baghdad's OK.
"We will continue to work very, very closely with our Iraqi partners on exactly who would be deployed, where they would be deployed and what kind of missions they would undertake," Kerry said.
Kerry said that the move to deploy Special Forces was not new but an extension of previous agreements with Iraq.
"It's the same mission, not a different one but we need to provide greater assistance in ways that meet with the Iraqi authorities consent and needs," he said.
For now, the new forces are expected to operate independently of the 50 special operation forces going into northern Syria to advise and assist forces there.