BAGHDAD - US officials are questioning Iraq about Iranian flights in Iraqi airspace suspected of ferrying weapons to Syrian President Bashar Assad, whose conflict with rebels threatens to drag his neighbors into a regional struggle.

Iraqi Prime Minister Nuri al-Maliki's government is close to the regional Shi'ite power Iran, Assad's main ally, and he has opposed demands by Sunni Arab Gulf nations that Assad step down to end the escalating conflict over his rule.

Three prominent US senators visiting Baghdad told Maliki that ties with Washington would be damaged if his government permitted Iran to use its airspace to deliver arms to Syria. One US official urged Baghdad to inspect the Iranian flights.

US State Department spokesman Patrick Ventrell said on Wednesday Iraq had a responsibility to continue with measures to prevent Iran shipping arms through its airspace.

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