Story highlights Joint Chiefs spokesman says plan "is not a change in mission nor is it a combat role"

U.S. currently has advisers assisting Iraqis in Irbil and

Joint Chiefs chairman: Sunni tribes fighting ISIS need Iraqi military support

ISIS has killed some 400 members of one Sunni tribe in Anbar in recent days

Pentagon officials are readying a plan that would deploy U.S. military advisers to the volatile Iraqi province of Anbar to advise and assist Iraqi security forces in a region currently dominated by ISIS militants.

"To be clear, this is not a change in mission nor is it a combat role, as they will be operating in the same advisory role as the other locations," Col. Edward Thomas, spokesman for the chairman of the Joint Chiefs of Staff, told CNN.

U.S. advisers currently operate in areas around Baghdad and Irbil in the north of the country. The new proposal would put U.S. troops in the middle of some of the most violent situations in Iraq.

Thomas said the plan is still "under development."

"From the beginning of the campaign, we have said that we would expand this type of support to the Iraqi government should they act in a manner that was representative of the security interests of all Iraqis," Thomas said.

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U.S. officials maintain that Iraqi support for Sunni tribes going on the offensive against ISIS will be a necessary part in the effort to defeat the militants, who are also called ISIL and refer to themselves as the Islamic State.

In a news conference with reporters Thursday, Gen. Martin Dempsey, the Joint Chiefs chairman, signaled the possibility of the new role when he said the Iraqi government had not yet requested U.S. military support in efforts to defend a Sunni tribe that has suffered mass executions at the hands of ISIS militants.

"That's why we need to expand the train-advise-and-assist mission into the Al- Anbar Province," Dempsey said. "But the precondition for that is that the government of Iraq is willing to arm the tribes."

Dempsey said the United States had "positive indications" the Iraqi government was prepared to do that, but had not yet acted.

Thomas said such a mission would hopefully open the door to the establishment of an Iraqi National Guard while also helping to push back ISIS control of the province.

There is no indication from Pentagon officials on when such a mission could begin.

Anbar was the scene of a bloody insurgency during the U.S.-led war in Iraq until an uprising by Sunni tribes in 2006 took hold to push out forces from al Qaeda's franchise in Iraq -- the precursor organization to ISIS.

Some 400 members of the Sunni Abu Nimer tribe in Anbar have been killed in recent days after rising up against ISIS rule in the province.