In a statement issued today, the US embassy said the delivery was made earlier this month in order to help bolster Iraq forces fighting a breakaway al-Qaida group known as the Islamic State of Iraq and the Levant.
The statement promised to send more weapons to Iraq in the coming weeks.
Since late December, Iraq's western cities have seen fierce clashes pitting government security forces and their allies from tribal Sunni militias against al-Qaida-linked militants and other insurgent groups.