Iraq says it's waiting for the U.S. to provide evidence that its airspace is again being used by Iran to ship weapons to Syria.

An Iraqi spokesman acknowledged that Iran is ferrying supplies through Iraqi airspace but said Tehran has assured Prime Minister Nouri al-Maliki that the flights contain food and other humanitarian aid for victims of Syria's civil war.

Spokesman Ali al-Moussawi said the U.S. has promised to provide proof that the Iranian flights are shuttling arms — a violation of a U.N. Security Council resolution.

Earlier this year, Washington pressured Iraq to stop any Iranian weapons shipments through its airspace.

Three U.S. senators visiting Baghdad Wednesday said the flights pose a renewed threat to Mideast stability.

The new flights were first reported by the New York Times.