Story highlights Tribal leader warns of a massacre if ISIS moves into Anbar province town

He says ISIS is gaining ground in the Iraqi province, which is just west of Baghdad

(CNN) An Iraqi tribal leader said Saturday that ISIS militants are gaining ground in Anbar province, predicting a "collapse within hours" of Iraqi army forces there if tribal forces withdraw.

Sheikh Naim al-Gaoud, a Sunni Muslim leader of the Albu Nimr tribe, called for more U.S. intervention -- including ground troops, arming tribes directly or at least pressuring the Iraqi government to give the tribes more firepower.

While U.S. officials have said that ISIS, which calls itself the Islamic State, is on the defensive in Iraq and Syria, al-Gaoud says that's definitely not the case where he is.

"In Anbar, we are losing ground, not gaining," he said.

Thousands of families had been under siege in the town of Jubbat al-Shamiya until getting help Friday from U.S.-led coalition airstrikes and Iraqi forces, according to al-Gaoud.