WASHINGTON — America’s top-ranked military officer says the surging Islamic State group has an “apocalyptic, end-of-days strategic vision” in the Middle East and cannot be defeated unless the United States and a coalition of partners confront it head-on in Syria.

“They can be contained, not in perpetuity,” said Army Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff.

The United States so far has restricted a series of airstrikes to Iraq, but concerns have increased as the Islamic militant group has extended its reach from safe havens in civil-war-ravaged Syria across the Iraqi border.

Appearing with Dempsey at the Pentagon Thursday, Defense Secretary Chuck Hagel credited U.S. bombing as well as U.S. arms supplies to Iraqi and Kurdish forces as key factors in the recapture this week of the Mosul Dam in Iraq that had been in the hands of the Islamic State militants.

Hagel said the U.S. airstrikes have helped Iraqi and Kurdish fighters regain their footing in Iraq.

Dempsey said that taking on the Islamic State more forcefully would not necessarily require airstrikes by the U.S. in Syria, although Hagel appeared to leave open that possibility by saying, “We’re looking at all options.”

Hagel said operations the U.S. military has undertaken so far “have stalled ISIL’s momentum and enabled Iraqi and Kurdish forces to regain their footing and take the initiative.” ISIL and ISIS are alternate acronyms for the Islamic State group that is an outgrowth of the al-Qaida terrorist network.