The Syrian government strongly denied it carried out a chemical weapons attack and the Organization for the Prohibition of Chemical Weapons said it has opened an investigation.
The Syria conflict was further complicated on Monday when unidentified war planes struck a Syrian air base near Homs, killing at least 14 people, including Iranian personnel.
The fast-paced developments threatened to further hike tensions between the USA and Russian Federation, which has in the past warned against any US military action against President Bashar Assad's government. It said there were several dead and wounded.
"Many dead, including women and children, in mindless CHEMICAL attack in Syria", he wrote in the first of three tweets.
Mr Trump and France's President Emmanuel Macron issued a joint statement on Sunday vowing to "co-ordinate a strong, joint response" to the alleged attack.
Russian U.N. Ambassador Vassily Nebenzia said on Monday that Moscow has warned the United States of "grave repercussions" if it carries out an attack against Syrian government forces over reports of a deadly chemical weapons attack.
"We express our readiness, after the liberation of Douma from militants, to immediately send Russian specialists in radiological, chemical and biological protection for the collection of data, that will confirm the fabricated character of these statements", Yevtushenko said.
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Russian Federation and Syria both offered during the U.N. Security Council meeting on Monday to take OPCW investigators to Douma.
Syria's state news agency SANA initially said the attack on the T4 air base was likely "an American aggression", but the Pentagon denied involvement, and the agency then dropped the accusation, blaming Israel instead. Some had bluish skin, a sign of oxygen deprivation. Dr. Muhammad, a doctor in Ghouta, said patients were coughing blood, a symptom not seen in previous chemical attacks.
The toll is likely to rise, said the Union of Medical Care Organizations (UOSSM), a group of global aid agencies. But it said the suffocations were the result of shelters collapsing on people inside them. It says they had been held by the Army of Islam group since 2013. In a statement, it said a fact-finding mission was gathering information from all available sources to establish whether chemical weapons were used.
Douma has been crippled by close to five years of siege by government forces.
Douma was once one of the hubs of the 2011 Arab Spring uprising against Assad's government.
In recent weeks, government forces have recaptured villages and towns in the eastern Ghouta suburbs of the capital. He repeated that he wanted the US military out of the country in a press conference on Tuesday. The US Department of Defence, however, denied government forces had launched any chemical attack.
The United States plans to call for a U.N. Security Council vote on Tuesday on a proposal for a new inquiry into responsibility for the use of chemical weapons in Syria, diplomats said.