CIA Director John Brennan arrived in Israel Thursday evening and held consultations on the situation in Syria, amid fears that Israel could get drawn into the fighting there.

Upon landing in the country, Brennan, whose visit was not announced ahead of time, went directly to the army headquarters in Tel Aviv for a meeting with Defense Minister Moshe Ya’alon, Channel 10 reported. During the meeting, the two shared intelligence assessments, and Ya’alon reiterated Israel’s refusal to let advanced weapons make their way from Syria to Hezbollah, vowing to continue carrying out strikes against arms shipments.

According to Israel Radio, the two also discussed Iran’s nuclear program and other regional threats.

Twice this month, Israel carried out air attacks in the Damascus area to blow up Fateh-110 ground-to-ground missile consignments en route to Hezbollah via Syria from Iran.

The meeting followed on the heels of Prime Minister Benjamin Netanyahu’s recent visit to Russia, during which he met with President Vladimir Putin and told him that Moscow’s sale of the S-300 missile defense system to Syrian President Bashar Assad could push the Middle East into war.

Russia’s Foreign Minister Sergey Lavrov, evidently unmoved by the dramatic Israeli warning, declared on Thursday that while Moscow was “not signing any new deals,” it would honor existing contracts with Syria, including for the transfer of the S-300 air-defense systems. “We’ve already carried out some of the deal,” Lavrov said, “and we will carry the rest of it out in full.”

In their talks, Netanyahu reportedly told the Russian president that the S-300 had no relevance to Assad’s civil-war battles against rebel groups, and implored Moscow not to deliver the systems, Channel 2 reported.

He said that if acquired by Assad, the S-300 — a state-of-the-art system that can intercept fighter jets and cruise missiles — “is likely to draw us into a response, and could send the region deteriorating into war,” the Channel 2 report said Tuesday.

An Israeli source was quoted Thursday as saying that Netanyahu had told Putin the S-300s represent a weapons system that “shatters [Israel's] qualitative edge,” presumably since it would greatly constrain the Israeli Air Force’s freedom of movement above Syria and neighboring Lebanon.

The Israeli source was also quoted as saying that Israel would “firmly oppose” the transfer of S-300s to Hezbollah in Lebanon.

On Wednesday, Israel reportedly warned Assad that further attacks were being considered, and that it would “bring down” his regime if he retaliated.

Also on Wednesday, Israel Radio reported that Tehran had approached Damascus about letting Hezbollah open a new front against Israel from Syrian territory.

The Lebanese daily al-Akhbar suggested last week that Iran had “reached a final decision” to respond to reported Israeli airstrikes on a weapons transfer in Syria by “turning the Golan into a new Fatah-land. The front has become open to Syrians and Palestinians and anyone who wants to fight Israel.”