White House spokeswoman Sarah Huckabee Sanders said Mr Trump held a meeting with his team to discuss the situation, but "no final decision has been made". "We are continuing to assess intelligence and are engaged in conversations with our partners and allies".
A statement released by the French President Emmanuel Macron, Friday, said that a "red line set by France in May 2017 has been crossed". The sites reportedly include "two Syrian airfields, a research center and a chemical weapons facility".
Asked about concerns in planning a strike on Assad's regime, Mattis cited worry over inadvertently causing civilian casualties and avoiding anything that would trigger a wider war. Syria's government and its allies seem more willing to fight back than they were a year ago, and that should give the Trump administration and our European allies pause. We have just absolutely decimated ISIS. "Could be very soon or not so soon at all!" he had tweeted.
Later he was noncommittal.
"We are obviously looking at that very closely".
Members of the Security Council vote after presentations for a resolution for an independent investigation on the use of chemical weapons in Syria during a Security Council meeting, April 10, 2018, at United Nations headquarters.
But Trump has long criticized his predecessor Barack Obama for failing to enforce a previous USA "red line" in 2013 after earlier chemical attacks blamed on Assad's forces.
But, the official added, Trump believes that in order to be able to negotiate successfully with Putin, it is essential that he demonstrate he is willing to take a harder line in Syria.
He added the the US and it's allies are prepared for "sustained" response until Syrian government stops use of chemical weapons.
After May met with her Cabinet, a spokesperson issued a statement saying it is highly likely that Syria's President Bashar Assad was responsible for Saturday's attack that killed dozens outside Damascus.
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"Cabinet agreed on the need to take action to alleviate humanitarian distress and to deter the further use of chemical weapons by the Assad regime". "What would happen next is hard to say. No local resident confirmed the chemical attack".
A fact-finding mission from the Organisation for the Prohibition of Chemical Weapons is expected to head to Douma. It was not clear whether the presence of the investigators could affect the timing of any USA military action.
You have more than 2,000 soldiers on the ground.
"The US - the possessor of the biggest arsenal of chemical weapons - has no moral right to blame other countries". But on a strategic level, the question "is how do we keep this from escalating out of control".
"I ordered the United States armed forces to launch precision strikes on targets associated with the chemical weapon capabilities of Syrian dictator of Bashar al-Assad", Trump said.
He is troubled by the similarly gruesome pictures of suffocating children, but his tougher stance this time is driven in part by his hardened view of Putin and his belief that Assad did not learn a lesson from the first strike, officials said. More broadly, he doubted the wisdom of bombing.
"I'm not going to say which day we absolutely knew that there was proof".
Trump also called out Russian Federation and Iran, asking how they could stand behind a leader like al-Assad.
Speaking to reporters in Moscow, Mr Lavrov reiterated a strong warning to the West against military action in Syria, saying it would increase flows of refugees into Europe.
Around 30 missiles were fired in the attack, and a third of them were shot down, the official added.