"We sent a letter which Minister Lavrov wrote to the OPCW director general with a full outline of our position and an explanation of why the activities of the so-called fact-finding mission in Syria do not suit us in its previous regime and previous methodology," Ryabkov told reporters Friday.
He said Russia submitted a draft resolution jointly with Iran for the OPCW Executive Council's consideration.
"Moscow believes that the conclusions formulated by the fact-finding mission in Syria are politically motivated, biased and requiring further clarification," Ryabkov said.
"The OPCW will resume its session on Wednesday. No decisions have been taken yet," Ryabkov told reporters.
OPCW Director-General Ahmet Uzumcu said Thursday he expected its fact-finding mission into the reported Khan Shaykhun attack to complete its work within the next two to three weeks.
Meanwhile, all permanent UN Security Council members should be included in the international chemical weapons watchdog's new expert group investigating the reported April 4 chemical attack in Syria, Russian Deputy Foreign Minister Sergey Ryabkov said.
"The mission should include representatives of those countries that can objectively assess the situation rather than follow the guidelines dictated by their governments. These are not just member states of the UN Security Council, but the permanent member states of the UN Security Council," Ryabkov told reporters Friday.
He said Iran, Brazil and India should also take part in the fact-finding mission into the reported attack in Khan Shaykhun.