Three US senators voiced concerns to Iraq's prime minister that Iran has resumed using Baghdad's airspace to fly weapons and equipment to bolster Bashar al-Assad's regime in Syria, they said on Wednesday.
Senators John McCain, Joe Lieberman and Lindsey Graham told reporters in Baghdad that while Tehran had told Prime Minister Nuri al-Maliki the planes were carrying humanitarian aid, the US believed they had military equipment on board.
Their comments came as the New York Times reported on Wednesday that Iran had resumed transporting the equipment, citing unnamed US officials, after the Islamic republic stopped such overflights earlier this year.
"We did raise concerns with the prime minister and the foreign minister (about overflights)," Lieberman said.
"The prime minister has said that he had testimony, or promises from the Iranians that they were just flying humanitarian assistance, but we believe otherwise.
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"I think we should present him (Maliki) with... as much evidence as we can, to show why we believe those Iranian cargo and commercial planes... are carrying items... that enable Assad to kill his own people."
McCain added that the issue was a violation of a UN Security Council resolution, and said Maliki told the senators that US Vice President Joe Biden had said Washington would provide Baghdad with proof regarding the cargo, but such evidence had not yet been handed over.
McCain said he believed the transport flights resumed after a July 18 suicide bombing on a heavily guarded security headquarters in Damascus killed four top regime officials, including defence minister General Daoud Rajha and Assad's brother-in-law, Assef Shawkat.
In March, Baghdad informed Tehran it would not permit arms shipments to Syria to pass through or over its territory after Washington said it was concerned about Iranian cargo flights through Iraqi airspace.
The US said at the time it had warned Iraq that the planes might contain arms that could be used by Damascus to crush the uprising in Syria.
At the time, Maliki insisted that all items transported through Iraq to Syria were humanitarian goods.