The Israeli military's estimate marked the first specific intelligence assessment of Syrian President Bashar al-Assad's military and weapons capabilities since a chemical attack on the rebel-held town of Khan Sheikhoun on April 4 killed some 90 people, including dozens of children.

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. One official added that Israel estimates that Assad still has "between one and three tons" of chemical weapons.

The Syrian president has strongly denied his forces were behind the gas attack, although Israel, along with the US and much of the international community, has accused the Syrian regime of carrying out the strike.

France's Foreign Minister Jean-Marc Ayrault said Wednesday that this country would present proof of the Assad regime's culpability in the coming days.

In response to the attack, the US fired 59 missiles at the Syrian air base said to be the launching pad for the chemical attack. Israel welcomed the strike on its neighbor.

"Israel fully supports President Trump’s decision and hopes that this message of resolve in the face of the Assad regime's horrific actions will resonate not only in Damascus, but in Tehran, Pyongyang and elsewhere,"  said a statement issued by the office of Israeli Prime Minister Benjamin Netanyahu.

Read more: Syria's chemical weapons, explained

Although Israel has largely remained on the sidelines of the six-year civil war in Syria, it has carried out a series of airstrikes on what it suspected were arms shipments sent from Iran bound for the Lebanese militant group Hezbollah.

Promises to dismantle nuclear arms

The Syrian regime had agreed to surrender its chemical weapons arsenal in 2013, in a bid to hold off US intervention in retaliation for a chemical attack on an opposition-held Damascus suburb earlier that year which killed hundreds and prompted worldwide outrage.

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 international supervision in 2014. However, doubts soon emerged over whether all of the regime's armaments or production facilities were declared and destroyed.

Read more: Opinion: Trump, Assad and international law

UK-based chemical weapons expert Dan Kaszeta told the Associated Press that Israel's estimate was conservative, but nonetheless was enough to be highly lethal.

"One ton of sarin could easily be used to perpetrate an attack on the scale of the 2013 attack," Kaszeta said. "It could also be used for roughly 10 attacks of a similar size to the recent Khan Sheikhoun attack."

dm/cmk (AP, Reuters)