Three senior defense officials, speaking on condition of anonymity, told reporters that Israeli intelligence believed Syrian military commanders had ordered the devastating attack with Assad's knowledge.
Western leaders including US President Donald Trump have accused Assad of being behind the attack in the rebel-held town, saying his forces used a chemical weapon during an air strike.
Laboratory tests later confirmed that victims of the April 4 attack were exposed to Sarin nerve gas or a similar banned toxin.
This comes two weeks after a chemical attack that killed almost 90 people in Syria.
The US has not ruled out additional strikes against the regime should it opt to use chemical weapons in the future.
Trump targets Canadian trade again, focused on energy, lumber, dairy
Fitzgerald says legislators will continue to press the Canadians until they get a good explanation for the policy shift. President Donald Trump has called protectionist trade measures by the Canadian government "a disgrace".
Meanwhile, Dan Kaszeta, a UK-based chemical weapons expert, told the AP that the Israeli estimate of Assad's chemical weapons cache appeared to be conservative, yet it was enough to be highly lethal.
The United States and many other nations have called the attack in the Khan Sheikhun area of Syria's southern Idlib province a chemical weapons attack and accused the Syrian government of responsibility.
"The process has resumed with 3,000 people leaving Foua and Kefraya at dawn, and almost 300 leaving Zabadani and two other rebel-held areas", SOHR's Rami Abdel Rahman told the AFP news agency. "Definitely, 100 percent for us, it's fabrication", he said. "While further details of the laboratory analyses will follow, the analytical results already obtained are incontrovertible", OPCW Director-General Ahmet Üzümcü said on Wednesday, addressing the organisation's executive council, which was held at The Hague, Netherlands.
The Syrian regime's stockpile of chemical weapons, which it disclosed amounted to some 1,300 tons of sarin, VX nerve agent and mustard gas, among other chemical agents, was said to have been dismantled and destroyed under worldwide supervision in 2014.
It was reported at the time that the entire stockpile was dismantled and shipped out of the country under global supervision in 2014, and was later destroyed.
Trump Draws the Line: It's 'Hollywood vs. Georgia' in June Runoff Election
The nearest Republican - former state secretary of state Karen Handel - came in at just 19.8 per cent. Jackson recorded a 45-second radio ad endorsing Ossoff that ran for several days before the election.
Syria has blamed terrorist groups for the attack, and Russian President Vladimir Putin suggested that the attack was carried out by "forces" trying to frame the regime of Syrian President Bashar al-Assad. But doubts began to emerge soon afterward that not all such armaments or production facilities were declared and destroyed.
Earlier on Wednesday, France said it has proof that the regime used chemical weapons in the attack on Khan Sheikhoun.
Israel and Syria have never had diplomatic relations, and a state of war has formally existed between the two since the formation of Israel in 1948.
All charges against the Syrian government over chemical weapons use are unsubstantiated and based on questionable social media materials, the Russian Foreign Ministry said in remarks published Thursday.
Britain's Theresa May announces shock elections on June 8th
Montgomeryshire MP, Glyn Davies, said the Prime Minister had been left with "little choice" due to frustration over Brexit. He said May simply sensed the chance to secure a majority of 100 MPs or more. "She expects a coronation and not a contest".
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