Israel on Wednesday deemed the Iranian pullout of heavy weapons to a distance of 85 kilometers from the Golan Heights border with Syria to be insuffcient.
Backed by Russia, Iran, and Lebanon's Hezbollah Shi'ite militia, Syrian President Bashar Assad has retaken territory in southern-western Syria from rebels, closing in on the Golan.
Moscow has sought to reassure Israel by saying it wants only Syrian forces to deploy on or near the Syrian-held Golan. Israel, however, insists that forces controlled by Iran, its arch-foe, exit Syria entirely now the civil war there is ending.
"The Iranians withdrew and the Shi'ite formations are not there," TASS news agency quoted Alexander Lavrentyev, President Vladimir Putin's special envoy to Syria, as saying.
Lavrentyev said Iranian service personnel whom he described as advisors could be among Syrian army forces who remain closer to the Israeli border.
"But there are no units of heavy equipment and weapons that could pose a threat to Israel at a distance of 85 km from the line of demarcation", Lavrentyev said.
Regional Cooperation Minister Tzachi Hanegbi told Israel Radio that the Iranian withdrawal was not enough, citing the longer-range threat posed by Iranian missiles or drones positioned in Syria.
"There'll be no compromises nor concessions on this matter," he said.
"What we have laid down as a red line is military intervention and entrenchment by Iran in Syria, and not necessarily on our border," Hanegbi stressed.
Last week an Israeli official, who spoke on condition of anonymity, said Russia had offered to keep Iranian forces at least 100 km from the Golan Heights ceasefire line.
Israel rejected the offer, which was made during a meeting between Prime Minister Benjamin Netanyahu and visiting Russian Foreign Minister Sergei Lavrov.
In an apparent riposte, Russia's ambassador to Israel, Anatoly Viktorov, said on Monday that Moscow could not compel Iran to leave Syria.
But Viktorov also signalled that Russia would continue to turn a blind eye to Israeli air strikes against suspected Iranian and Hezbollah arms transfers or emplacements in Syria.
Hanegbi said Israel wanted to prevent Iran and Hezbollah from effectively extending their Lebanese front against it.
"We are not ready to see a new Hezbollah front on our northern border between Israel and Syria. This is something that is dangerous. This is something that, if we don't prevent it today, when still at its outset, will a exact a heavy price of us down the line," he said.