The alleged chemical weapons attack in the city of Douma this past weekend, which has left dozens dead, seems to offer proof that Trump's 2017 strike failed to act as a warning against further chemical weapons use.
A Lebanese politician with close links to the Syrian government confirmed that precautionary measures were being taken throughout Syria.
Trump said his decision could come as early as the end of Monday or within the next 48 hours.
Last week Trump said he wanted to pull USA troops out of Syria, though his advisers have urged him to wait to ensure Islamic State militants are defeated and to prevent Assad's ally Iran from gaining a foothold there.
The president consulted other world leaders about holding Mr. Assad accountable for the atrocity Sunday that killed dozens in Douma, a rebel-held suburb of Damascus.
Mr Trump revealed the U.S. is "trying to get people" into Syria as he asked: "If they're innocent, why aren't they allowing people to go in and prove?"
President Trump is scrapping plans to travel this week to a summit in South America because of the situation in Syria, the White House said Tuesday. Mr. Trump has promised a "forceful" response in Syria.
U.S. President Donald Trump has chose to cancel his first official trip to Latin America this week in order to focus on responding to a suspected chemical weapons attack in Syria, the White House said on Tuesday.
Nebenzia, reflecting earlier warnings from President Vladimir Putin's Kremlin, said: "From what we hear now, I am afraid they are looking for a military option, which is very, very risky". "All options are on the table, but I'm not going to get ahead of what the President may or may not do".
A Syrian air base was struck by missiles a little more than 24 hours after the alleged chemical attack, an airstrike that Syria and Russian Federation have blamed on Israel.
Trump also called out Russian President Vladimir Putin for his role in Syria's conflict that just entered its eighth year. The U.N. chemical weapons watchdog has started an investigation. "Russian Federation wants to undermine our interests at every turn".
President Donald Trump says the USA has many military options as it decides how to respond to an apparent poison gas attack in central Syria that killed more than 40 people.
If the United States proposal is put to a vote, it would likely be vetoed by Russian Federation.
That attack prompted the USA to launch several dozen Tomahawk cruise missiles at a Syrian air base.
As a permanent member of the UN Security Council, Russia can veto any substantive resolution.
The Prime Minister rang both the US President and France's Emmanuel Macron in a frantic round of diplomacy over the suspected chemical attack in Douma.
"I'd like to begin by condemning the heinous attack on innocent Syrians with banned chemical weapons", Trump said.
Top U.S. military chiefs reportedly advised the president that their forces need to remain in Syria to prevent an ISIS resurgence.
Vladimir Shamanov, a retired Russian general who heads the defense affairs committee in the lower house of parliament, said in televised remarks that a USA strike in Syria could hurt Russian service members and trigger retaliation.
"If it's Russian Federation, if it's Syria, if it's Iran, if it's all of them together, we'll figure it out", he said.
Potential preparations for a military ramp-up in Syria come just over a week after Trump signalled he wants to end USA involvement in the Middle Eastern country.
Last year, Trump ordered strikes on a Syrian airfield in response to another chemical weapons attack, though that assault lasted only a matter of hours.
With those high-level talks proceeding, Mrs. Sanders said, the president will not attend the eighth Summit of the Americas in Lima, Peru, or travel to Bogota, Colombia, as planned.
In remarks Monday night as he met with military leaders at the White House, Trump suggested a military strike against Syria was imminent.
The Department of Defense would not reveal whether the drones affected by Russia's jamming are crashing, citing operational security, but an unnamed official told NBC that it is having an "operational impact" on US military operations.
Israel's foreign ministry says Tuesday that Syria "continues to perpetrate crimes against humanity in using these outlawed weapons".
"The council can not allow a situation of uncontrollable escalation in Syria on any front", he said.