The United States accused the Syrian government on Friday of utilizing banned chemical arms at least 50 times since Syria’s civil war started seven years ago — far higher than the number of attacks that had been publicly confirmed.
The accusation, made by the American ambassador to the United Nations, Nikki R. Haley, came during a vitriolic exchange with her Russian counterpart at a meeting of the Security Council, which focused on a suspected chemical weapons assault in a Damascus suburb last week.
President Trump has expressed outrage over the deadly assault in the suburb, Douma, and threatened a military response. When that might happen remains unclear.
Without elaborating on the sources of her information, Ms. Haley said the American government had estimated that the forces of President Bashar al-Assad of Syria have utilized chemical weapons “at least 50 times” since the war began.
The use of chemical weapons is a war crime.
“Our president has not yet made a decision about probable action in Syria,” Ms. Haley told the council. “But should the United States and our allies decide to act in Syria, it will be in defense of a principle on which we all agree.”
The Russian ambassador, Vasily A. Nebenzya, accused the United States and its allies of reckless Middle East warmongering by threatening Syria with military force.
Mr. Nebenzya also said there was no confirmed evidence that chemical weapons had been utilized in the April 7 Douma attack, and that the United States and its allies had “demonstrated they have no interest in an investigation,” although international chemical weapons inspectors have been sent to Syria to conduct an inquiry.
The Russian envoy also asserted that Russia, Mr. Assad’s biggest ally, had done far more than the West to achieve peace in the Syria conflict. He accused Washington of having adopted “a categorical policy to unleash military force against Syria.”
Mr. Trump’s threats of a strike on Mr. Assad’s forces, the Russian envoy said, were “unworthy of a permanent member of the Security Council.”
Ms. Haley said she was incredulous at Mr. Nebenzya’s defense of the Syrian government and his overall portrayal of events. “I’m in awe of how you say what you say with a straight face,” she told the Russian ambassador.
Ms. Haley called the use of chemical weapons in Syria “a violation of all standards of morality.”
Referring to the Douma assault, Ms. Haley said: “We know who did this. Our allies know who did this. Russia can complain all it wants about fake news, but no one is buying its lies and its cover-ups.”