Lieberman said the alleged attack in the neighbouring country was carried out "on the direct and premeditated command of Syrian President Bashar al-Assad with Syrian planes."
"I say this with 100 per cent certainty," Lieberman told the Yediot Aharonot daily, according to excerpts from an interview published on the paper's website.
He did not say what his certainty was based on.
At least 86 people were killed on Tuesday in rebel-held Khan Sheikhun in Idlib province in the suspected chemical attack.
Britain, France and the United States yesterday held off calling a vote at the UN Security Council on a resolution demanding an investigation after Russia suggested it would veto it.
Asked whether Israel should be more directly involved in the war in Syria, Lieberman replied, "Why would it be up to us to do the work of others? It is the responsibility of the international community."
Israeli Prime Minister Benjamin Netanyahu said the world must act to rid Syria of chemical weapons.
Israel has sought to avoid being dragged into the six-year Syrian conflict, but has acknowledged carrying out strikes to stop advanced weapons deliveries to Hezbollah, with whom it fought a devastating war in 2006.
Assad is supported by Israel's enemies Iran and Lebanese movement Hezbollah.
Russia also supports Assad and Netanyahu has held a series of talks with President Vladimir Putin in recent months to avoid accidental clashes in Syria.
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