(CBS) -- Russia all but dismissed Wednesday a report by United Nations weapons inspectors who visited the Damascus suburbs to investigate the facts surrounding an Aug. 21 chemical weapons attack, and said Syria had handed over evidence allegedly showing it was rebel forces who carried out the attack.
The U.S., Britain, and France, along with many other nations and global organizations, concluded even before the U.N. report was published on Monday that Syrian President Bashar Assad's military fired the rockets containing sarin gas into the Ghouta suburbs early that morning.
U.S. Ambassador to the U.N. Samantha Power said the "technical details" in the 41-page U.N. inspectors' report "make clear that only the regime could have carried out this large-scale chemical weapons attack."
"It's very important to note that the regime possesses sarin," added Power, "and we have no evidence that the opposition possesses sarin."
Russian Foreign Minister Sergey Lavrov made it clear Tuesday that Moscow, however, remains unconvinced, calling for the Ghouta attack to be "impartially, objectively, professionally investigated."
He argued that the Syrian regime's claim it was rebels who launched the poison gas attack could not be dismissed based on the evidence available. "The truth has to be determined," said Lavrov.
His deputy, Sergei Ryabkov, visited Damascus on Wednesday and was reportedly handed Syria's own packet of "evidence" which shows the rebels carried out the poison gas attack.
Ryabkov told Russian media the material handed to him by the Syrians, "bears witness to the rebels participating in the chemical attack," but he said Russia had not yet come to a final conclusion on who was to blame for the Ghouta strikes, which left more than 1,400 people dead according to the White House.
None of the details of that evidence have been provided, but the Assad regime has repeatedly denied any use of chemical weapons and blamed the Ghouta attack, and previous alleged uses of chemical weapons during the two-and-a-half year conflict, on the rebels.
"We are disappointed, to put it mildly, about the approach taken by the U.N. secretariat and the U.N. inspectors, who prepared the report selectively and incompletely," Ryabkov told Russian state-run news agency RIA.
"Without receiving a full picture of what is happening here, it is impossible to call the nature of the conclusions reached by the U.N. experts ... anything but politicized, preconceived and one-sided," Ryabkov said after meeting his Syrian counterpart Walid al-Moallem.
Ryabkov's remarks reinforced the extent to which Russia is likely to resist efforts by the U.S. and France to include a use-of-force clause in the U.N. resolution being hammered out this week in the Security Council on a plan to seize and destroy Syria's vast chemical weapons stockpile.
France and the United States insist a military option remains on the table, and they are pushing for the U.N. resolution to include harsh punishment for the Syrian regime should it fail to live up to its end of the bargain.