About 85 percent of the dead were civilians killed by the forces of the Syrian government and its allies, the Observatory said.
Haley's statement follows French President Emmanuel Macron's statement on Monday that France would launch attacks on any Syrian facilities used to launch chemical weapons attacks, much as the USA did in April 2017.
She vowed to close any room for evasion, though it is unclear how it could win the backing of Russian Federation, which has used its veto power to protect the Syrian government in the past.
Haley accused Syria and its allies Russian Federation and Iran of exploiting such "loopholes" to "continue starving and pummeling hundreds of thousands of innocent Syrian civilians" in Ghouta, the last opposition-controlled pocket near Damascus.
Lavrov made the comments on March 13, after the United States said it was ready to act in Syria to end chemical attacks and "inhuman suffering" if Russia, Iran, and Syria continue to allegedly ignore the truce approved two weeks ago.
Without offering concrete evidence, General Valery Gerasimov also claimed that Syrian militants are planning to stage a "provocation" involving the use of chemical weapons in order to justify what he said would be a subsequent US strike on government-held neighborhoods in Damascus.
Man with a child are seen in hospital in the besieged town of Douma, Eastern Ghouta, Damascus Thomson Reuters One of the last pockets of Syrian rebels has been holding out in eastern Ghouta against a furious onslaught of Russian and Syrian airstrikes that have killed 1,160 people since February 18, according to a war monitor.
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Sexton picked up back-to-back offensive fouls early, resigning him to the bench for most of the first half. The Virginia Tech Hokies (21-11) are coming from a 71-65 loss to Notre Dame in the ACC tournament.
"It's not the path we prefer, but it's a path we've demonstrated we will take, and we are prepared to take it again", Haley concluded. But on Monday, the U.S. State Department said it was very concerned by the violence and called an "urgent meeting" in Jordan to ensure maintenance of the de-escalation zone.
UN Secretary-General Antonio Guterres briefed the council on Monday on the implementation of the resolution but Russian Federation has said the ceasefire could not be imposed by the Security Council without a deal between the warring parties, while Damascus argues that a ceasefire ordered by the UN Security Council protects members of terrorist groups in eastern Ghouta.
He did not say when the alleged attack would take place or provide detailed evidence to back his assertions.
Calling the situation a calamity growing more desperate by the day, Guterres said the Syrian government and its allies - an oblique reference to Russian Federation and Iran - had intensified their offensive so much that they have increased the territory they control in the enclave from 10 percent barely a week ago to 60 percent today.
Syria's United Nations ambassador, Bashar Jaafari, said terrorists had conducted chemical attacks on civilians and staged it to make it look like the Syrian military was to blame. He urged council members not to abandon efforts to implement a cease-fire. "When we gave this information to Washington, they said that "it was no longer necessary" and immediately conducted a strike", the minister added.
The assault on Ghouta is one of the heaviest in the war, which enters its eighth year this week.