Carter`s visit is his second to Iraq as Pentagon chief since he took office in February.
His visit came as the Iraqi security forces were battling IS extremists in the city of Ramadi, the capital of Anbar province, where hundreds of U.S. Marines as military trainers and advisers were stationed.
The security situation in Iraq has drastically deteriorated since June 2014, when bloody clashes broke out between Iraqi security forces and the IS militants.
The IS took control of the country`s northern city of Mosul and later seized swathes of territories in Nineveh and other predominantly Sunni provinces.
A U.S.-led international coalition has been conducting air strikes on IS targets in both Iraq and neighboring Syria.
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