Baghdad is "looking the other way" as Iran sends military equipment through Iraqi airspace to Syrian President Bashar al-Assad's regime amid the ongoing conflict in Syria, a U.S. official said.
The official, who spoke on condition of anonymity, called on Iraq to randomly search Iranian planes flying to Syria, and said Washington had complained to "all levels of the Iraqi government" about the lack of inspection.
"It's reasonable to stop the planes and inspect them," the official said, according to the AFP news agency.
"At least do some randomly and legitimately to see. They (Iraq) have cause to be suspicious. Instead, they are suspending their disbelief, looking the other way, and averting their gaze."
"If they really wanted to find out they would stop flights randomly, periodically, and actually look at them. And we are confident that they would find, and we have told them this, military equipment and weapons, ammunition, those type of things," he said according to the news agency.
Asked who in the Iraqi government Washington had spoken to about its concerns, the US official replied, "All levels of the Iraqi government."
The United States has persistently called on Iraq to inspect Iranian planes flying to Syria via Baghdad's airspace, despite Iranian insistence that they are only carrying humanitarian supplies.
Iraq has publicly announced having searched two planes, both in October.
The New York Times reported in December that Iran appears to have been forewarned by Iraqi officials as to when plane inspections would be conducted, thus helping Tehran avoid detection.
Iran has remained a steadfast ally of Assad's regime despite the conflict in his country, which, according to the United Nations, has killed more than 70,000 people since it erupted in March 2011.