Russia will not deliver fighter planes or other new weapons to Syria while the situation there remains unresolved, the deputy director of a body that supervises Moscow's arms trade was quoted as saying on Monday.
"While the situation in Syria is unstable, there will be no new deliveries of arms there," Vyacheslav Dzirkaln told journalists at the Farnborough Airshow in Britain, Russia's Interfax news agency reported.
The refusal to send more arms to Syria could signal the strongest move yet by Moscow to distance itself from Syrian President Bashar al-Assad, whom it has defended in the UN Security Council from harsher sanctions.
It could also scuttle up to $4 billion of outstanding contracts, including fighter jets and air-defence systems that were expected to be delivered this year.
A spokesman for Dzirkaln's Federal Service for Military Technical Co-operation would not confirm the deputy director's comments when contacted by telephone. Reuters was awaiting for a response to requested written questions.
In Washington, White House spokeswoman Erin Pelton said it would be a positive development if confirmed.
"We refer you to Russian authorities for confirmation," she said. "If it is truly Russia's intention to halt arms sales to Syria, then we would laud this step and commend Russia for this measure, which would send a strong signal to the Assad regime."
"We have long called on all nations to cease supplying this regime with weapons, given its continued use against the Syrian people."
Although legal, Russia's arms trade with Syria has fueled concerns that Moscow is supplying Assad with weapons being used against protesters taking part in an armed uprising against him.
Russian President Vladimir Putin has said the arms Moscow delivers cannot be used in civil conflicts and Foreign Minister Sergei Lavrov has said the supplies are defensive weapons sold in contracts signed long ago.
US Secretary of State Hillary Clinton has termed Russian statements that the weapons are unrelated to the violence in Syria "patently untrue" and Washington has called the delivery of a shipment of heavy Russian weapons "reprehensible".
Dzirkaln was quoted as saying that Russia, one of Syria's main weapons suppliers, would not be delivering a shipment of 36 Yak-130 fighter planes, a contract for which was reportedly signed at the end of last year.
"In the current situation, talking about deliveries of airplanes to Syria is premature," he said.
Rosoboronexport, Russia's monopoly arms exporter, would not comment on Dzirkaln's remarks, which were also reported by the Russian state news agency RIA.
"We understand the position of (the agency), but we are a separate organisation and will not comment," said spokesman Vyacheslav Davidenko.
Syria's arms-trade ties with Moscow date back to the Soviet era. It has previously signed contracts worth billions of dollars and hosts a Mediterranean supply-and-repair facility that is Russia's only naval base outside the former Soviet Union.
A Russian analyst said Moscow had already distanced itself from Assad.
"Russia has stopped signing new contracts with Syria and is delaying the shipments of already signed contracts," said Ruslan Aliyev, an expert on the Russian-Syria arms trade at the Moscow-based defence think-tank, CAST.
"It's basically a political decision based on Moscow's view of Syria."
Russia faced Western criticism last month after Clinton said Russian attack helicopters were on the way to Syria. Moscow said they were part of an old contract and that it only provided weaponry that could be used against external aggression.
"Previously, we were fulfilling old contracts, including repairs of the machines," Dzirkaln said. "Until the situation stabilises, we will not carry out any new arms deliveries."