BAGHDAD - Kurdish officials this fall took delivery of three planeloads of small arms and ammunition imported from Bulgaria, three U.S. military officials said, an acquisition that occurred outside the weapons procurement procedures of Iraq's central government.

The large quantity of weapons and the timing of the shipment alarmed U.S. officials, who have grown concerned about the prospect of an armed confrontation between Iraqi Kurds and the government at a time when the Kurds are attempting to expand their control over parts of northern Iraq.

Neighboring countries with large Kurdish minorities, including Turkey and Iran, have said they would oppose the emergence of an independent Kurdistan, as the autonomous region is known.