Iraqi forces repelled an
Assailants with suicide vests led the assault, which involved 20-25 Islamic State fighters, some wearing Iraqi military uniforms, Rear Adm. John Kirby told reporters in Washington.
No U.S. combat personnel were involved in the battle at Al Asad Air Base, the spokesman said.
"At no time were U.S. troops anywhere near the fighting," said Kirby, who added that U.S. personnel were "at least a couple of miles" away. "So they might have heard shots being fired, but that would have been about it."
The air base, in a remote desert area of Iraq's western Anbar province, is a sprawling facility about the size of Boulder, Colo., that was a major hub for American forces during the 2003-2011 U.S. occupation of Iraq. Almost 800 Iraqi troops are training at the base, the Pentagon said in a statement.
The attackers on Friday reached the perimeter of the facility, Kirby said, but it was not clear whether the base was breached. At least eight assailants were reported killed. There was no definitive word on Iraqi military casualties.
The attempt to storm the base came after the militants launched an attack on a nearby town, Al Baghdadi, according to Iraqi media accounts.
In a statement apparently related to Friday's attack, Prime Minister Haider Abadi stressed Baghdad's "concern" for Anbar, a largely Sunni province where Islamic State, a radical Sunni group, has considerable support.The province was also a hotbed of opposition to U.S. forces during 2003-2011.
"We confirm that there is no need for the presence of foreign fighting forces, neither in Anbar nor anywhere else in Iraq," the prime minister said on his official website.
There are currently some 2,575 U.S. troops in Iraq, but none in direct combat roles, U.S. authorities say. The troops are there to advise, train and otherwise assist the Iraqi military, the Pentagon says.
Islamic State controls wide areas of Iraq and neighboring Syria. Months of U.S.-led bombardment have slowed and in some cases reversed the militants' advance. But Islamic State remains a formidable, well-armed foe with substantial civilian support in Anbar and elsewhere in Iraq and Syria. President Obama has vowed to "degrade and ultimately destroy" the group.
Times staff writers McDonnell reported from Beirut and Hennigan from Washington. Special correspondent Nabih Bulos in Beirut contributed to this report.