He spoke after US Defence Secretary Chuck Hagel said the Obama administration was "considering all different options" following a reported chemical attack it alleges was launched by Damascas.
Pledging to maintain Russia's non-interventionist position on the UN security council, Mr Lavrov (pictured below) said: "Washington, London and Paris say they have incontrovertible evidence that the Syrian government is behind the chemical attack in Damascus, but they have not yet presented this evidence."
UN inspectors "have the mandate to determine if chemical weapons were used and, if so, which ones, but not who unleashed this attack," he added.
His comments came as UN inspectors attempting to access the site of an alleged recent chemical weapons attack were forced to turn back after coming under attack.
Their convoy travelling with Syrian government permission to the site where around 300 people were reported killed last week was fired on by unidentified snipers.
Spokesman Martin Nesirky said a clearly marked UN vehicle leading a convoy was "deliberately shot at multiple times."
He added that the inspectors remained "determined to carry out the mission" but added that "all sides need to extend their co-operation so they can conduct this work safely."
German government spokesman Steffan Seibert said that if inspectors confirmed the use of chemical weapons "it must be punished."
And Turkish Foreign Minister Ahmet Davutoglu said his country could join a coalition against Syria without a UN mandate.
Opposition forces were reported to have taken control of the town of Khanasir, cutting off a government supply route between Aleppo and the central city of Hama.
The pro-rebel Syrian Observatory for Human Rights claimed that the gain would leave the Syrian army under siege in Aleppo.