The Organization for the Prohibition of Chemical Weapons said Syria used the chemical weapons sarin and chlorine in a series of attacks in 2017.
The Syrian government began deploying on Monday in a major victory for President Bashar al-Assad and his principal ally Russia.
The 2020 Democratic presidential contender said she wants to stop politicians from “fighting in these wasteful regime-change wars."
Roughly 7,000 Syrians will retain legal status in the U.S. for another 18 months.
The State Department said Washington would "respond quickly and appropriately" if Assad was found to have launched a chemical weapon attack.
The figure is hundreds more than the number the U.S.-led coalition claims over the entire four-year campaign against IS, the groups said.
The democratic presidential hopeful said the Syrian ruler should be held accountable "if the evidence is there" on chemical weapons.
The congresswoman and Democratic presidential contender was engaged in a tense discussion on "Morning Joe."
Syrian President Bashar al-Assad's government is liable for $302.5 million in damages, a judge ruled.
Trump's Syria pullout endangers the Kurds, Arabs and Christians who've fought ISIS — but they've got more on their minds than U.S. policy.