The officials said they were "confident" in the intelligence though not 100 percent sure, NBC News said on its website.
"We have a number of options", said White House spokeswoman Sarah Sanders, "and all of those options are still on the table". The only objective of this action is to accuse the Syrian authorities as well as Russian Federation of committing this crime and use it as a pretext for armed intervention against legitimate Syrian government.
Early Saturday morning, State TV also broadcast footage of hundreds of Syrians demonstrating against the USA and its allies in the landmark Omayyad Square in Damascus. A USA -led coalition has launched thousands of airstrikes - mostly on Islamic State and other extremist rebels.
This was stated by the press service of the White house.
Later Thursday he was noncommittal.
The U.N. Security Council, tasked with maintaining global peace and security, has been riven, with Moscow virulently denying the Douma attack took place, or postulating that it was carried out by rebels.
In terms of responsibility, Trump said: "If it's the Russians, if it's Syria, if it's Iran, if it's all of them together, we'll figure it out". "I think the USA has an obligation to lead an global response to hold people accountable for that", Ryan told reporters.
UK Prime Minister Theresa May said in a statement that she "authorized British armed forces to conduct co-ordinated and targeted strikes to degrade the Syrian Regime's chemical weapons capability and deter their use".
A former officer in Syria's chemical program, Adulsalam Abdulrazek, said Saturday the joint U.S., British, and French strikes hit "parts of but not the heart" of the program. Initial reports indicated the use of chlorine gas, possibly in addition to the nerve agent Sarin.
The public suggestion of United States military confrontation with Russian Federation is sure to raise tensions in an already volatile situation and add more confusion to U.S. policy in the region.
The Russian military said it observed movements of USA naval forces in the Gulf.
Defense Secretary James Mattis said Wednesday that the US and its allies are mulling how to respond to the attack.
At the Pentagon, the director of the Joint Staff, Lt. Gen. Kenneth McKenzie, said the more than 100 missile strikes delivered a blow to the "heart" of Syria's chemical weapons network. That warning was made in order to avoid casualties among Russian military advisers in Syria.
Cafarella said the United States must decide how far it wants to go in terms of hitting Iranian proxy forces near U.S. positions in eastern Syria, or even targeting Russian-supported facilities.
Both Trump and his defence secretary Jim Mattis abruptly cancelled upcoming travel plans Tuesday, as the USS Donald Cook - a guided-missile destroyer - moved to within striking range of Syria.
Labour chief Jeremy Corbyn warned "more bombing, more killing, more war will not save lives, it will take lives and spawn the war elsewhere".
Connable warned that if the USA accidentally or purposefully kills uniformed Russian soldiers, there would potentially be a unsafe escalation between the two nuclear powers.
At stake in Syria is the potential for confrontation, if not outright conflict, between the US and Russian Federation, former Cold War foes whose relations have deteriorated in recent years over Moscow's intervention in Ukraine, its interference in the 2016 USA presidential election and its support for Syrian President Bashar Assad.
Pushkov added that the U.S. can not reverse or change the conflict in Syria without sending several tens of thousands of its soldiers there.
"We'll be making some major decisions over the next 24 to 48 hours", Trump said during a Cabinet meeting a day after saying there would be "a big price to pay" by Syria and Assad.
"Our relationship with Russian Federation is worse now than it has ever been, and that includes the Cold War", Trump said.
"I'm not ready to speculate that that would happen", Mattis said.