The United States said Friday it is concerned about Iranian cargo flights over Iraq to Syria, saying it has warned Iraq they might contain arms that could be used by Damascus to crush protests.

"Without getting into intelligence matters, we are concerned about the overflight of Iraq by Iranian cargo flights headed to Syria," State Department spokeswoman Victoria Nuland told reporters.

"We are consulting with Iraq about them and we are making the point that any export of arms or related materials from Iran, frankly, to any destination would be a violation of UN Security Council resolution 1747," she said.

Nuland said the Iraqis were also being told "that any arms sent to the Syrian regime at this time would obviously be used in the brutal repression that the regime is exacting on its own people."

She added: "So we are in consultation with Iraq... encouraging the government of Iraq to be absolutely sure about any cargo that is overflying its territory."

Iraqi Premier Nuri al-Maliki insisted Friday that all items transported through Iraq to Syria were humanitarian goods, after a US newspaper reported Iran was moving weapons to Syria via Iraqi air space.

"Iraq does not allow its land or its skies to be a passage for weapons in any direction, and from any source," Maliki said in a statement released by his office.

He said shipments going through Iraq were "only carrying humanitarian goods, not weapons."

Maliki said Iraq was "pushing towards finding a political solution to the Syrian situation... (and) to avoid more bloodshed."

The Washington Times reported on Thursday that Iraq refused "several" US requests to stop Iranian cargo flights bound for Syria, citing an unnamed US official.

The newspaper said Iraq was made aware of intelligence obtained through intercepted air traffic communications that the planes were transporting weapons, and added that the United States requested Iraq either stop the flights or allow them to be inspected.