She said Russian Federation would ensure the monitors' security.
Sergey Lavrov did not specify which agency or provide evidence, but he warned the West against proposed military action.
An extraordinary meeting of the Council of the State Duma, which will consider the draft federal law "On measures of influence (counteraction) to unfriendly actions of the United States and (or) other foreign states", its to take place on April 16.
Douma and the sprawling eastern Ghouta region near the capital, Damascus, had been under rebel control since 2012 and was a thorn in the side of Assad's government, threatening his seat of power with missiles and potential advances for years. Over 13,000 militants and their family members are said to have been evacuated from Douma since April 1. This is in contrast to an incident one year ago in which the USA government had video and other evidence of certain aspects of an actual attack by Syrian aircraft, which involved the use of sarin gas.
They are also said to be considering charging United States airlines for using Russian airspace.
Macron said Thursday that France would not tolerate "regimes that think everything is permitted".
A state broadcaster is telling Russians to stockpile food and water in preparation for war as the conflict in Syria escalates.
On Wednesday, the UN's World Health Organization demanded access to verify reports from its partners, which include Sams, that 70 people had died - including 43 who showed "symptoms consistent with exposure to highly toxic chemicals".
Russia, a key Syrian ally, dismissed the allegations against Syria and said its own experts found no "trace of chlorine or any other chemical substance used against civilians". She said she spoke Thursday with French President Emmanuel Macron.
Earlier this week, Trump tweeted that the relationship between the USA and Russian Federation was at its worst point in history, including the Cold War, and hinted at possible mutual efforts to prevent a new arms race.
On Wednesday, he again warned Russian Federation of being an ally of the Assad regime.
Asked to comment on possible US strikes, President Vladimir Putin's spokesman said Thursday that "it's necessary to avoid any steps that may fuel tensions in Syria".
The head of the Liberal Democratic Party of Russia, Vladimir Zhirinovsky, added that the import restrictions on United States goods and services would not be applied to purchases made by individuals, but rather on wholesale batches.
"The danger of escalation is higher than simply Syria because our military is there".
Trump was reacting to a warning from Russian Federation on Tuesday that any USA missiles fired at Syria over the deadly assault on a rebel enclave would be shot down and the launch sites targeted.
The U.S., United Kingdom and France are all North Atlantic Treaty Organisation members.
The bill, which follows the latest round of U.S. sanctions on Russian Federation, was drafted on Friday jointly by State Duma speaker Vyacheslav Volodin and the heads of all four parliamentary caucuses.
Erdogan said he'll talk to Putin later on Thursday, a day after he talked to President Donald Trump about Syria. In the years since, Russian Federation has invaded and annexed regions of several nations, including Georgia and Ukraine; and they've waged information warfare campaigns against the United States and our allies in Europe and the Baltics.
Critics assailed Trump for the limited nature of the 2017 attack, which did little to disrupt Syrian air operations or deter the use of chemical weapons, reported repeatedly in the following months.
The U.S. and its allies threatened military action after an alleged gas attack by government forces over the weekend that Syrian opposition activists and medics say killed more than 40 people.