MOSCOW Information that the United States has given Russia about suspected use of chemical weapons by Syrian President Bashar al-Assad's forces "does not look convincing", President Vladimir Putin's senior foreign policy adviser said on Friday.
Yuri Ushakov said expanded U.S. military support for Assad's opponents would undermine joint efforts to organise a peace conference, but added that Moscow was "not yet" considering sending Assad advanced S-300 anti-aircraft missile systems in response.
A U.S. official said on Thursday that President Barack Obama had authorised sending U.S. weapons to Syrian rebels for the first time, after the White House said it had proof that the Syrian government had used chemical weapons against opposition forces.
U.S. officials briefed Russia on the information they had, Ushakov said at a briefing before Putin's trip to Northern Ireland for a G8 summit. "But I will say frankly that what was presented to us by the Americans does not look convincing."
"It would be hard even to call them facts," said Ushakov, speaking at a briefing before a summit where Putin will meet Obama and other Western leaders.
"If the Americans ... carry out more wide-scale aid to the rebels and opposition, it will not make organising the international conference easier," he said.
But he said Russia was not "competing" with the United States over Syria. Asked whether Moscow would send Assad the S-300 missile systems that Israel and the West have urged it not to deliver, he said: "We are not talking about that yet."
Russia and the United States are trying to bring Syria's government and rebels together for talks, but have not secured a commitment from either side to participate.
(Reporting by Alexi Anishchuk; Writing by Thomas Grove; Editing by Steve Gutterman and Kevin Liffey)