The agreement was reached at the end of November, the documents showed, just weeks after Iraq's Prime Minister Nouri al-Maliki returned from Washington, where he lobbied the Obama administration for extra weapons to fight al Qaeda-linked militants.

Some in Washington are nervous about providing sensitive U.S. military equipment to a country they worry is becoming too close to Iran. Several Iraqi lawmakers said Maliki had made the deal because he was fed up with delays to U.S. arms deliveries.