The United States plans to buy arms for Sunni tribesmen in Iraq including AK-47s, rocket-propelled grenades and mortar rounds to help bolster the battle against Islamic State militants in Anbar province, according to a Pentagon document prepared for Congress.

The plan to spend $24.1 million represents a small fraction of the larger, $1.6 billion spending request to Congress focusing on training and arming Iraqi and Kurdish forces.

But the document underscored the importance the Pentagon places on the Sunni tribesmen to its overall strategy to diminish Islamic State, and cautioned Congress about the consequences of failing to assist them. […]