Censor.NET reports referring to a statement by Secretary of State Rex Tillerson.
"We call upon Russia and Iran, yet again, to exercise their influence over the Syrian regime and to guarantee that this sort of horrific attack never happens again," the statement reads.
"As the self-proclaimed guarantors to the cease-fire negotiated in Astana, Russia and Iran also bear great moral responsibility for these deaths," Tillerson adds.
He also called upon Moscow and Tehran to refrain from "illusions" about the Syrian president.
"Those who defend and support him, including Russia and Iran, should have no illusions about Assad or his intentions. Anyone who uses chemical weapons to attack his own people shows a fundamental disregard for human decency and must be held accountable," the secretary of state says.
U.S. President Donald Trump has also blamed the Bashar Assad regime for the chemical attack, calling it a consequence of the Obama administration's wrong actions.
Earlier, Western media, referring to The Syrian Observatory for Human Rights, reported that warplanes belonging to Russia or the Syrian government committed a chemical airstrike on the city of Khan Sheikhoun in the northwestern province of Idlib. As noted, the attack killed at least 58 and injured dozens of people.
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