A joint military operation, possibly with France rather than the U.S.in the lead, could send a message of global unity about enforcing the prohibitions on chemical weapons and counter Syria's political and military support from Russian Federation and Iran. The sites reportedly include "two Syrian airfields, a research center and a chemical weapons facility".
Mr Trump's latest intervention came after he previously tweeted that missiles "will be coming".
Sanders adds that USA officials are "continuing to assess intelligence" and are "engaged in conversations with our partners and allies".
Theresa May received unanimous cabinet backing for United Kingdom military action against Syrian regime targets after senior ministers were briefed by Sir Mark Sedwill, the national security adviser, on the intelligence case pointing to President Assad's culpability for the Douma attack.
The UN Security Council, tasked with maintaining worldwide peace and security, has been riven, with Moscow virulently denying the Douma attack took place, or postulating that it was carried out by rebels.
He said: "Parliament must be consulted on this".
And in a new twist to the unfolding diplomatic drama, US President Donald Trump issued a fresh tweet saying: "Never said when an attack on Syria would take place". Trump on Wednesday had warned Russian Federation to "get ready" for a missile attack on its ally Syria.
Brexit Secretary David Davis said: "It is a very, very delicate circumstance, and we've got to make this judgment on a very careful, very deliberate, very well thought-through basis, knowing exactly ... how strong the evidence is".
Trump has since tempered those remarks and the White House said no final decisions on possible actions had been taken. Then Thursday he tweeted that an attack on Syria "could be very soon or not so soon at all!" In Syria, this instinct points him away from a military-centric answer to Assad, writes Bonnie Kristian.
The BBC said May was ready to give the go-ahead for Britain to take part in action led by the US without seeking prior approval from parliament, and the Financial Times said the cabinet had agreed to this.
Macron doesn't need parliamentary permission to launch an operation.
"The Syrian government denies responsibility".
Mattis said he personally believes Syria is guilty of an "inexcusable" use of chemical weapons, while noting that the global fact-finding team would likely fall short of determining who was responsible.
France already has some 1,100 troops involved in its Operation Chammal, created in 2014 to fight Islamic State extremists in Iraq and extended in 2015 to Syria, as part of the US -led coalition. This is in contrast to an incident one year ago in which the USA government had video and other evidence of certain aspects of an actual attack by Syrian aircraft, which involved the use of sarin gas. Multiple IS terror attacks have targeted France, including one last month.