Kremlin spokesman Dmitry Peskov said Wednesday that Russia hopes all parties involved in Syria will avoid any steps that could "significantly destabilize" an already "fragile situation".
The US has pledged to punish President Assad harshly for a suspected poison gas attack on the town of Douma, in the eastern Ghouta region near the Syrian capital on Saturday.
"We stand ready to provide military options if they are appropriate as the President determined", he said.
The World Health Organization says patients at health facilities showed "signs of severe irritation of mucous membranes, respiratory failure and disruption to central nervous systems of those exposed". The regime has been accused of using chemical weapons against civilians, most recently in the attack on Douma that killed at least 42 people.
Will Trump assemble a coalition to respond to Assad?
Reports suggested that more than 500 people, mostly women and children, were taken to medical centres with breathing problems, foaming at the mouth and with burning sensations in the eyes. But the deterrent effect of U.S. attacks on the regime's chemical campaign has saved lives in the last year, and could save more lives going forward. Two irreconcilable things have been thrown into the scale: the posture of a strong leader and the danger of an armed conflict between Russia and the US.
Earlier in the day, Trump held a meeting with members of his cabinet where he told reporters that his administration would be making "some major decisions over the next 24 to 48 hours" regarding the response to Syria. Based in The Hague in the Netherlands, the group is independent but it often collaborates with the United Nations.
The French president, who said he was in daily contact with President Trump, said any strikes would go after Syria's "chemical capabilities".
The United States is circulating a draft resolution in the Security Council, calling on Syria to facilitate access so the OPCW team can visit the sites to collect soil samples and interview witnesses, according to a copy viewed by The Washington Post.
Parliament is in recess until Monday, though it could be called back early for an emergency debate. Opposition and rescuers allege that the Syria government dropped barrel bombs from helicopters loaded with chemical agents.