The Obama administration on Friday accused Russia of pursuing a "morally bankrupt" policy in Syria, following Turkey's seizure of alleged Russian military equipment from a Syrian plane headed from Moscow to Damascus.
The State Department said it had "grave concern" that Russia is continuing to supply Syrian President Bashar Assad's regime with materiel that could be used to bolster its fight against rebels.
"We have no doubt that this was serious military equipment," State Department spokeswoman Victoria Nuland told reporters, referring to the cargo that was taken from the plane.
Turkish fighter jets on Wednesday intercepted the Syrian Air flight from Moscow and seized what it said what it said was ammunition and military equipment for the Syrian Defense Ministry.
But Russian Foreign Minister Sergey Lavrov said the plane was legally carrying Russian radar parts for Syria.
Lavrov insisted the shipment of "electric equipment for radars" was legitimate cargo that complied with international law, but he added that it was of "dual purpose," meaning it could have civilian and military applications. Syria has branded the incident piracy and Russia said the action endangered the lives of Russian citizens aboard the aircraft.
The U.S. acknowledges the shipments are legal but only because Russia along with China, has repeatedly blocked efforts to impose sanctions, including an arms embargo, on the Assad regime at the U.N. Security Council.
Russia and China have been harshly criticized for their stance by the U.S. and its allies, and Nuland took that criticism a step further on Friday.
"There are no Security Council sanctions on Syria because Security Council members Russia and China continue to block them," she said. "Everybody else on the Security Council is doing what it can unilaterally to ensure that the Assad regime is not getting support from the outside."
"No responsible country ought to be aiding and abetting the war machine of the Assad regime and particularly those with responsibilities for global peace and security as U.N. Security Council members have," she said. She added that the shipment was "legally correct but the policy is still morally bankrupt."