U.S. Secretary of State John Kerry is set to meet his Russian counterpart late Thursday in Geneva, as international negotiations intensify to get Syria to dismantle its chemical weapons arsenal.
Officials traveling with Kerry said he will emphasize with Sergei Lavrov a U.S. demand for Syrian President Bashar al-Assad to quickly account for all of his chemical stockpiles. U.S. officials said the meetings could last several days.
President Barack Obama said he hopes the Kerry - Lavrov meeting will "yield a concrete result."
Mr. Assad told Russian state television he has agreed to give up his chemical weapons because of a request from Russia, his longtime ally, and not due to threats from the United States.
The Syrian president said his government will submit documents to join an international convention banning chemical weapons in a few days and will provide information about the stockpiles one month after joining the treaty.
A U.N. spokesman later told reporters that the world body has received a letter from Syria to start the disarmament process of filing documents towards joining the international convention.
U.S. officials have said the Russian proposal for securing and destroying the Syrian weapons is possible but "difficult and complicated."
In other developments, Obama administration officials told several U.S. news organizations that the Central Intelligence Agency has begun delivering light weapons to moderate Syrian rebels for the first time in Syria's conflict.
But Free Syrian Army rebel chief Salim Idris appeared to dispute that claim, telling U.S. broadcaster NPR that his fighters have not received "any weapons from our American friends."
It was not clear if the claimed CIA deliveries were made directly by American personnel or via a third party.
Russian President Vladimir Putin used an opinion piece in the New York Times newspaper to warn the United States against conducting military strikes against the Assad government, a longtime Russian ally.
President Barack Obama has threatened "limited" military action to punish the Syrian government for allegedly carrying out a chemical attack that killed hundreds of civilians near Damascus last month. But he also has called for more diplomacy before deciding on such a step.