Prime Minister Benjamin Netanyahu will fly to Russia to meet with President Vladimir Putin next week to discuss the escalating crisis in Syria and other issues, Russian media reported Saturday.

Netanyahu is understood to be deeply concerned about the prospect of Moscow selling President Assad sophisticated S-300 missile defense systems. The long-range ballistic system, which can down both fighter planes and intercept cruise missiles, would represent a significant upgrade for Syria’s already formidable air defenses.

Putin’s press secretary, Dmitry Peskov, confirmed Saturday that Netanyahu was planning to visit Russia next week. He added that the two leaders had conversed by phone on May 6 and discussed Syria’s weapons caches. The phone call took place after Israel last weekend reportedly bombed targets around Damascus where parts of a consignment of Iranian Fateh-110 missiles, en route to Hezbollah via Syria, were being stored.

Russia’s RIA Novosti news agency reported that Netanyahu and Putin would meet in Sochi, on the Black Sea coast.

A diplomatic source told the news agency that the visit was “currently in the planning stages.” 

On Friday, Russia’s foreign minister defended his country’s potential sales of antiaircraft systems to Syria, insisting they are defensive systems and not banned by international law.

Speaking in Warsaw, Sergey Lavrov appeared to avoid saying clearly whether Moscow would sell Syria advanced S-300 batteries.

The foreign minister emphasized that Russia is not planning to supply Syria with any weapons beyond current contracts that are nearing completion, Russia Today reported.

Israel has asked Russia to cancel what it says is the imminent sale of S-300 batteries to the Syrian government, arguing it would complicate the situation. Netanyahu, who returned from China on Friday, was immediately reported planning to fly to Moscow to ask Putin to scrap any delivery of S-300s.

Asked by reporters whether Russia is planning to supply the S-300, Lavrov said somewhat unclearly: “Russia is not planning to sell. Russia has been selling for a long time, has signed contracts and is completing deliveries of technology that consists of anti-aircraft systems.”

Lavrov said the weapons are to help Syria defend itself against air attacks.

Israel suspects that Russia plans to sell Damascus six S-300 missile batteries, as well as 144 missiles, the Wall Street Journal reported Thursday.