"Iran is already well on its way to controlling Iraq, Yemen and to a large extent is already in practice in control of Lebanon," Netanyahu told Russian President Vladimir Putin as they met in Russia's Black Sea resort of Sochi on Wednesday.
The visiting PM, who was hoping for a sympathetic response from Putin, was left disappointed as the Russian head of state refused to address his claims.
Russia and Iran have helped the government of Syrian President Bashar al-Assad score major victories in the years-long fight against foreign-backed terror groups in the conflict-ridden Arab country.
Moscow has been running an aerial campaign against terror positions across Syria since 2015.
It has also separately pushed through with a plan alongside Iran and Turkey to set up four de-escalation zones throughout Syria, where airstrikes would be halted.
The three countries have been mediating talks between the Syrian government and opposition in the Kazakh capital of Astana since January.
Israel is critical of the efforts, fearing that they would ultimately cement Iran’s position as a powerful regional player and benefit Islamic resistance movements such as Lebanon’s Hezbollah, which is also involved in the anti-terror campaign.
That probably explains why the Israeli military has been carrying out airstrikes and shelling attacks against both Syrian government forces and Hezbollah fighters, while providing shelter and medical assistance to terrorists on the Syrian border.
Iranian President Hassan Rouhani said in June that the terrorist operations across the Middle East were part of Israel’s agenda and threatened the territorial integrity of all regional countries.