"We say enough with death, enough with killing civilians", said Hani Atassi, president of the Syrian American Council chapter in Chicago.
Inspectors from the Organisation for the Prohibition of Chemical Weapons (OPCW) are now in Damascus and are expected to visit Douma this weekend.
"Will this deter Assad from using chemical weapons again?"
Russian Federation in November used its veto three times to bury a previous UN-led inquiry which found that Syrian forces had used sarin in the attack on Khan Sheikhun in April a year ago.
Trump noted that a million people died or suffered injuries from chemical weapons during World War I. Since that time, he said, the civilized world has shunned the use of such weapons.
Haley said that the United States would not pull its troops out of Syria until its goals were accomplished.
"It's illegal because he didn't come and ask permission", he said.
In Damascus, Russia's news agencies reported that Assad told a group of Russian lawmakers that the Western missile strikes were an act of aggression.
Syria released video of the wreckage of a bombed-out research lab, but also of Assad arriving at work as usual, with the caption "Morning of resilience" and there were no immediate reports of casualties.
Britain's U.N. Ambassador Karen Pierce blamed Russian Federation for repeatedly vetoing resolutions on the use of chemical weapons in Syria and said Britain took military action "to save lives", on the legal basis of "humanitarian intervention".
The ministry reported that a total of 100 cruise and air-to-surface missiles had been fired (while 59 missiles were fired at the Shayrat Airbase last year), a lot of them were shot down by Syria's air defense units upon approaching their targets.
The United States, Britain and France have all participated in the Syrian conflict for years, arming rebels, bombing Islamic State fighters and deploying troops to fight the militants.
But until this weekend, they have refrained from targeting Assad's government, apart from a volley of United States missiles a year ago.
A number of non-governmental organizations, including the White Helmets, earlier said chemical weapons had been used in Douma, Eastern Ghouta, on April 7.
Sarin had previously appeared to be the threshold for intervention.
French Foreign Minister Jean-Yves Le Drian said in an interview published Sunday in the Journal du Dimanche newspaper that "we should join our efforts to promote a political process in Syria that would allow a way out of the crisis".
McKenzie said the Him Shinshar chemical-weapons storage facility near Homs was hit by 22 missiles.