Iraq stopped and searched a Syria-bound Iranian cargo plane for weapons on Tuesday, but allowed it to continue as no prohibited items were found, Iraqi officials said.

Washington has been pressuring Baghdad to ensure that all Iranian planes flying through its airspace are ordered to land and checked for weapons. This is the first time Iraqi officials have said that they have done so.

"We requested an Iranian cargo plane to land and it responded and was searched by air cargo specialists and security agencies," Nasser Bandar, the head of Iraq's civil aviation authority, told AFP.

"We did not see anything contrary to the instructions banning the transport of weapons between the Syrian and Iranian sides, so we therefore allowed it to continue its trip," he said.

A high-ranking Iraqi official told AFP that the aircraft was bound for Damascus from Tehran.

State Department spokeswoman Victoria Nuland said: "We regard it very positively that the Iraqi government is taking steps to investigate cargo overflying its territory headed for Syria."

"Our hope is that these kinds of cargos will be regularly inspected, and that will be a deterrent to folks abusing Iraqi airspace to get weapons into Syria," she added.

Meanwhile, a diplomat at the Iranian embassy confirmed Iraqi authorities had ordered an Iranian cargo plane to land at Baghdad airport and searched the aircraft, which belongs to Iran Air.

On September 21, Iraq denied permission for a North Korean aircraft to cross its airspace on its way to Syria over suspicions it would carry arms and advisers there.

Iraq has pointedly avoided calling for the departure from office of Syrian President Bashar al-Assad, who is locked in a bloody civil war with rebels opposed to his regime, and has instead urged an end to violence by all parties.