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Senior defense officials confirmed Monday that the al-Assad airbase in Iraq, where U.S. military are training Iraqi security forces, has been pounded almost daily by mortar attacks from ISIS militants, but claimed the attacks have been "completely ineffective."

Col. Steve Warren described the routine barrage of mortars aimed at al-Assad as "nuisance attacks." He said "no U.S. personnel or U.S. equipment" have come under direct fire at the base.

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There are currently 320 Marines located at al-Assad airbase north of Baghdad to train, advise and assist Iraqi security forces. The Marines are also training some 200 Sunni tribesman who have joined the fight against ISIS. The total number of American military on the ground is expected to reach 3,000, as authorized by President Obama, by early spring.

In addition, there are 170 soldiers from the Army's 1st Infantry Division training Iraqi security forces in Taji, southwest of Baghdad.

There are currently 2,140 American soldiers and Marines in Iraq. Eight hundred are protection forces, providing security for the U.S. embassy and military personnel and training Iraqi security forces at several locations in Iraq. Two new training facilities at Irbil and Besmaya are expected to open within weeks.

Col. Warren repeated today that no U.S. service members have been engaged in combat or been wounded by enemy fire and that all U.S. military personnel have the "inherent right of self-defense" should they come under attack.

—Jim Miklaszewski and Oliver Cox

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