ISTANBUL -- Some Sunni tribal leaders in Iraq's Anbar province who the U.S. have enlisted to fight against the Islamic State group are actually working with the Islamic State group, providing it with weapons and other materials, according to Sunni fighters in Anbar. The weapons were taken from Iraqi military stockpiles that were replenished by the U.S. and given to ISIS militants who are fighting to gain ground around the Ain al-Asad air base, where about 1,400 U.S. troops are stationed.

Sheikh Ali Hatem al-Suleiman, the leader of one of the largest Sunni tribes in Anbar, the Dulaim, is said to be working directly with the Islamic State group. Al-Suleiman has been an active opponent of the Iraqi government, especially when Prime Minister Nouri al-Maliki, a Shiite, held office.

Several other Sunni leaders from Anbar have been linked to al-Suleiman's work with ISIS, and several arrest warrants have been issued by the Anbar police. These Sunni tribal leaders are not only able to acquire weapons to give to ISIS but can also send money by working with wealthy Sunni businessmen such as Khamis al-Khanjar and Imad Mohammadi, who previously gave financial support to anti-government demonstrators in several parts of Iraq.

Currently, between 5,000 and 7,000 Islamic State group fighters from Anbar tribes are moving against the city of Fallujah, Majid Hussein, a political analyst based in Erbil in Iraqi Kurdistan, said. When they will have gained ground there, they will mount a push for Baghdad, he said.

The U.S. is currently supplying the Iraqi military with weapons and is advising its soldiers on fighting the Islamic State group. But the U.S. also intends to directly arm Sunni tribes in the province and to develop a Sunni-dominated national guard made of tribesmen.

In an effort to repeat the success of the “Sunni Awakening” strategy in 2007 that funneled arms to Sunni tribes in western Iraq to stop al Qaeda, the U.S. has enlisted tribal leaders to halt the Islamic State group with American weapons. Although those weapons have yet to reach the tribes in Anbar, any cooperation between tribal leaders and ISIS will likely hinder the U.S. strategy and risk exposing Baghdad to attack from ISIS.

The U.S. State Department said the support is part of the Overseas Contingency Operations' Iraq Train and Equip Fund, which allocates money to the Iraqi military, to the Kurdish military, and to training and equipping tribal forces. As part of the fiscal year 2015 budget, the U.S. allocated more than $24 million of the fund to tribal security forces, according to State Department documents. About $18.5 million was allocated to a force of tribal fighters in Anbar recruited through a mobilization program designed by the Iraqi government.

A U.S. State Department spokesman said Friday in response to a request from International Business Times that none of the millions of dollars allocated to the Iraq Train and Equip Fund have been used to provide the tribes with equipment so far. “Since the approval of [the funds] and the apportionment of the first 25 percent of funds, we are beginning to implement acquisition packages that support these initial requests, which include basic soldier items, rifles and other weapons, and ammunition,” the spokesman said. “The United States has obtained the commitment of the Government of Iraq … to secure the equipment received from the U.S. in a fashion consistent with U.S. practices.”

The State Department also told IBTimes that U.S. Central Command and U.S. security cooperation personnel in Iraq "are responsible for performing routine and specialized monitoring of end use with Iraqi Security Force personnel. If we were to hear reports that U.S.-origin equipment is being misused or provided to unauthorized users, we would engage the Government of Iraq in conjunction with the U.S. Embassy up to the highest levels to address any confirmed issues."