He added that "as far as the interests of Israel are concerned, it is best for you that Assad stay because most of the opposition representatives are Islamists and they told us openly that the first thing they would do when they are in charge would be to declare war on Israel".
Iran's accelerated attempt to establish a military presence in Syria, the prime minister said after the meeting, "attests to Iran's aggression, which has not lessened in the wake of the  nuclear agreement".
Israeli Prime Minister Benjamin Netanyahu met today (Wednesday) with Russian President Vladimir Putin in the resort town of Sochi on the shores of the Black Sea.
"We had the expectation that a deal between Trump and Putin would deal with the Iranian threat on our border", Ya'alon said in an interview in Tel Aviv. Both Russia and Iran back Syrian President Bashar al-Assad in his six-year civil war against armed Syrian rebels. Israel has been pushing the USA, and now Russian Federation, not to support a peace deal in Syria that allows Iran and the Iranian-backed Hezbollah terror group to keep boots on the ground.
Americans and Russians were focused on establishing safe zones in the region in order to concentrate on defeating the Islamic State while Israel thought, tactically, the powers should be focused on a longer term strategy and removing Iran's influence from the region.
Israel accuses Iran of building military bases and carving out a land corridor to transfer arms and fighters from Tehran to Beirut.
An Israeli media report noted that the delegation shared "sensitive, credible and deeply troubling intelligence", showing the expanding deployment of Iranian forces in Syria, which estimates put at 500 Iranian army soldiers, 5,000 Hezbollah fighters and several thousand guerrillas from Afghanistan, Pakistan and Iraq.
Israel argued that, if Iran remained in Syria, it would become a base for missiles being launched into Israel and Jordan. "An Iranian military presence in Syria will be a constant source of friction and tension not only with Israel, but with the Sunni majority in Syria, with the Sunni countries in the region, and with Sunni minorities outside the region". What it might do is "let Iran strengthen its positions in western Syria", further from Israel, he said.
"We can not forget for a single minute that Iran threatens every day to annihilate Israel", Netanyahu said.
Israel has come out clearly against the cease-fire brokered in Syria between Russian Federation and the United States, fearing that it will enshrine a permanent Iranian military presence in the country.
While Israel has rarely acknowledged carrying out its own airstrikes in Syria, numerous raids on weapons transfers have been attributed to Jerusalem.