In a statement on Wednesday, the Foreign Ministry said Russia would be represented by its ambassador to Iran, Levan Dzhagaryan, "if the meeting in Tehran really takes place".
It said Russia had received an invitation but that plans to hold the meeting on Thursday meant "time for the necessary preparations is very short".
The Foreign Ministry declined to comment further on Thursday.
"Naturally, we intend to firmly pursue our line (calling for) an immediate end to bloodshed and the suffering of the civilian population, as well as for achieving a peaceful resolution in the interest of all Syrians through a broad political dialogue," the statement said.
Russia has shielded Syrian President Bashar al-Assad from concerted pressure by joining China in blocking three Western-backed United Nations Security Council resolutions aimed to end 17 months of bloodshed, including one last month that would have threatened the government with sanctions.
Russia says it is not propping up Assad and would accept his exit from power in a political transition decided by the Syrian people, but that his departure must not be a precondition and he must not be pushed out by external forces, including the Security Council.