Russian Federation has been a key backer of Syrian President Bashar Assad, providing air cover for his offensive against the Islamic State group and Syrian rebels.
Analysts answered five key questions about what to expect next.
The military can also fasten "smart" guidance kits on existing "dumb" missiles to outfit them with the capability to hit specific targets.
Tomahawk cruise missiles, first used by the U.S. military during Desert Storm, maneouver easily and fly low to hit targets.
A joint military operation, possibly with France rather than the U.S.in the lead, could send a message of worldwide unity about enforcing the prohibitions on chemical weapons and counter Syria's political and military support from Russian Federation and Iran.
As it looked to head off the threat of Western strikes, Syria said it had invited the OPCW to visit the site of the alleged attack in Douma, a town in the Damascus suburb of Eastern Ghouta that is on the verge of falling to the regime after a long and bloody siege.
This time the Tomahawks may be relied on again, analysts said.
"She's telling us how to fight ISIS", Trump said of Clinton during the duo's first debate in the fall of 2016.
The USS Donald Cook, an Arleigh Burke-class guided-missile destroyer, is within easy striking range of Syria, as is a French frigate with its own cruise missiles.
In a tweet responding to the threat, President Trump said: "Russia vows to shoot down any and all missiles fired at Syria". Others said they have readied underground basements for cover. "So the U.S. military may decide to use a different method".
But it remains unclear if the United States knows where these are stored in Syria, Ashraf noted.
A World Health Organization statement on Wednesday did not confirm outright that a chemical weapons attack had taken place.
It came nearly exactly a year after a chemical attack in the northern Syrian town of Khan Sheikhoun killed dozens of people. Something I doubt any other president would have done.
The Pentagon said it would not comment on potential future military operations.
Ashraf suggested the USA would likely keep its warplanes and naval vessels out of proximity to Russian forces.
"Trump himself has in the past repeatedly criticized other US leaders for telegraphing actions to adversaries, and he refused to offer advanced details, for example, on his strategy for dealing with North Korea".
Shortly after his tweeted warning to Russia, Trump took a more conciliatory tone in lamenting that the U.S. -Russia relationship "is worse now than it has ever been". That warning was made in order to avoid casualties among Russian military advisers in Syria.
Trump previous year ordered a strike against Assad following a deadly sarin gas attack on the rebel-held town of Khan Sheikhun. We tell them. We're sending something else.
Trump did not detail what a strike on Syria would look like, or whether these would be US missiles. Trump also wrote back then. "But Russia has not used this system in Syria yet", he said.
The Russian Defence Ministry said yesterday: "We are attentively tracking the situation unfolding around Syria and in the whole region". Sandy Winnefeld, the targets are likely to be more valuable.
"If the Russians are true to their words, some of those missiles will be intercepted".