The opposition Syrian National Council (SNC) has rejected claims its fighters used chemical weapons in an attack in March.
The coalition on July 10 called the charges "desperate and fabricated."
Russia's UN Ambassador Vitaly Churkin made the accusation
on July 9 when he handed over an 80-page report assembled by Russian specialists who had visited the Syrian town of Khan al-Assal, near Aleppo, where 26 people were killed on March 19.
Churkin said evidence obtained by Russian experts showed the rebels fired a missile with sarin gas at the town.
A statement from the SNC said questioned "evidence provided by parties that support [Syrian President Bashar al-]Assad's tyrannical regime with money, weapons, and ammunition."
The SNC and other Syrian opposition groups accuse the Assad regime of using chemical weapons.
Based on reporting by AP and Interfax