The attack against a Syrian air base was the first USA assault against the government of President Bashar Al Assad.
Two US Navy destroyers in the Mediterranean Sea fired 59 Tomahawk cruise missiles at Shayrat air base in western Homs province at about 04:40 Syrian time (01:40 GMT) on Friday.
The move was welcomed by the Syrian opposition and its main backers, including Turkey and Saudi Arabia, but harshly condemned by Russian Federation and Iran, who back Mr Al Assad.
"There's always a transformation that takes place from a person who wins the presidency, and then once he assumes office he necessarily sees the world from a different perspective", said Edward Djerejian, a former US ambassador to Syria and Israel who now directs Rice University's Baker Institute for Public Policy. Secondly, we don't see a peaceful Syria with Assad in there.
He said the best outcome would be a peace agreement that leads to a transitional government accepted by all Syrians, followed by elections.
The UK's ambassador said President Assad had been "put on notice" and claimed Moscow had been left humiliated by its failure to bring him to heel. This is not, after all, the first time chemical weapons have been used in Syria and he himself urged Obama not to take action the last time round.
President Hassan Rouhani said the committee should be impartial and "must not be headed by Americans".
Britain's Foreign Secretary Boris Johnson has cancelled a scheduled visit to Moscow next week, his office announced Saturday, saying "developments in Syria have changed the situation fundamentally".
NEW airstrikes have targeted a town in Syria devastated by a chemical attack earlier this week, with Russian planes believed to be responsible. Trump said Assad's forces launched a gruesome chemical weapons attack from the site earlier in the week.
He had planned to travel to Russia Monday on a trip meant to start a fresh dialogue with Moscow.
US Secretary of State Rex Tillerson, in Florida to attend a summit between Trump and China's Xi Jinping, is due in Moscow next week for talks with President Vladimir Putin.
Xi agreed to increase China's cooperation with the USA to pressure North Korea to end their nuclear program, Tillerson said. Russian Federation may seek to improve Syria's surface-to-air missile system in the wake of this United States attack but it would be very much a case of shutting the stable door after the horse has bolted.
If Putin is looking for a way to even the score, it might not be in Syria, said Julianne Smith, a former National Security Council and Defense Department official now at the Center for a New American Security. He added that the United Nations was "created to support America instead of serving the wronged people".
America's top diplomat also says that the top USA priority in the region hasn't changed and remains the defeat of Islamic State militants. The groups Raqqa is Being Slaughtered Silently and Sound and Picture said the attack killed a woman and her six children.
Democratic Rep, Betty McCollum called on GOP House Speaker Paul Ryan to call the House back from its two-week recess to set clear limits on the use of US troops.
At least four civilians were killed with some putting the death toll as high as 15.
Cairo - Arab League chief Ahmed Abu Gheit warned on Saturday against a "dangerous escalation" in Syria after a U.S. missile strike on a Syrian airbase following an alleged regime chemical attack.
The news agency reported that during the Friday phone call, the Saudi monarch congratulated Trump for his "courageous decision".