The chairman of the U.S. Joint Chiefs of Staff, Gen. Martin Dempsey, left the door open Thursday to stepped-up U.S. military involvement in Iraq if ISIS militants pose a threat to the United States.

In response to a question about what the U.S. end game is in Iraq, Dempsey began by saying the U.S. military's current role is much different from it was during the Iraq war.

"Assessing and advising and enabling are very different words than attacking, defeating and disrupting," he said during a briefing at the Pentagon in Washington. "We may get to that point if our national interests drive us there, if (the Islamic State in Iraq and Syria) becomes such a threat to the homeland that the President of the United States, with our advice, decides that we have to take direct action. I am just suggesting to you that we are not there yet."

Dempsey also disputed the use of the term "mission creep" in Iraq.

"That's the wrong phrase. The issue is mission match," he said.

"We will match the resources we apply with the authorities and responsibilities that go with them based on the mission we undertake, and that is to be determined."

Barzani: It's time for referendum on independence

Masoud Barzani, the President of Iraq's semiautonomous Kurdish region, told the regional parliament Thursday that it is time to hold a referendum on the independence of Kurdish areas.

He said Kurds should no longer have to wait on anybody to obtain the right of independence and told the Kurdish parliament to begin taking steps to hold the referendum.

Last week, Barzani announced that disputed areas, including Kirkuk, were henceforth part of the Kurdish autonomous region, after the Iraqi central government failed to hold a long-awaited referendum.

Last month, the Iraqi army withdrew from Kirkuk, and Kurdish Peshmerga forces took control of the city and small villages in the areas as ISIS carried out its lightning offensive.

The move by the Kurds will probably complicate efforts to get Iraqi lawmakers to form a new government representing all three major population groups -- Sunnis, Shiites and Kurds.

Official: Nuns, orphans missing

Two nuns, who were thought to be under house arrest by ISIS militants, and three orphans have gone missing from an Assyrian Orthodox church in central Mosul, the governor of Nineveh province and witnesses told CNN on Thursday.

Militants believed to be from the Islamic State in Iraq and Syria initially barred the nuns from leaving Miskintah Church in the Khazraj neighborhood in early June, Gov. Atheel al-Nujaifi said.

The two nuns manage an orphanage on the church grounds, and both are very well known to Mosul residents, the residents say.

Residents in the neighborhood who were in touch with the nuns told CNN they had not been able to reach them on their cell phones since Tuesday. On Thursday, the residents forced their way into the church and said they could not find the nuns or three orphans.

The two nuns were identified by the governor and the residents as Sister Hannah and Sister Uttor.

Indian nurses being moved

Forty-six Indian nurses being held by ISIS in former Iraqi leader Saddam Hussein's hometown of Tikrit are being moved north, to the city of Mosul, which is under control of the militant group, Syed Akbaruddin, the spokesman for India's Ministry of External Affairs, said Thursday at a news briefing.