President Bashar Assad is lying if he says he has taken delivery of a first shipment of Russian-manufactured state-of-the-art anti-aircraft missiles, Israeli military sources said Thursday.

They were responding to reports that the Syrian leader had claimed in a TV interview that the first such missiles were now in his possession. It later turned out that Assad’s actual comments differed from excerpts the TV station conducting the interview had sent in a text message on Thursday morning, and were vaguer than reported.

According to a Channel 2 report, the officials said that Russia has yet to transfer any S-300 missile shipments to Syria and that, public statements notwithstanding, Moscow might not do so. Other Hebrew media outlets quoted unnamed Israeli officials echoing the same assertion, and describing Assad as “bluffing.”

American officials quoted by AP said they had no evidence that the Assad regime had received a shipment of S-300s. Two senior US officials also told Fox News that Assad doesn’t yet have the advanced Russian surface-to-air missiles.

The Israeli sources also said that Syria has only paid for a third of the S-300 contract. They added that even if the deal is eventually honored, it would take months for the S-300 batteries to be operational.

“It is not clear to me that the Russians are interested in transferring the weapons. Right now, it’s more of a threat,” said Ehud Ya’ari, Channel 2′s veteran, well-connected commentator.

In the remarks initially reported, Assad was erroneously said to have boasted that his country had received the first batch of missiles from Russia, and to have asserted that “the rest of the load will arrive soon,” in an interview with Hezbollah’s Al-Manar television broadcast Thursday night and reported early Thursday by Lebanese daily Al Akhbar.

Russia’s declared intention to deliver the sophisticated system, which can intercept fighter jets and cruise missiles, has created a tense standoff between Israel, Syria, and Russia, with Israel threatening to do “whatever it takes” to prevent the weapons being deployed, and Syria responding that it would retaliate in kind for any Israeli strike.

Ya’ari said Syrian-Israeli tensions had now reached “a sensitive, indeed incendiary” situation. In the Thursday TV interview, Ya’ari noted, Assad “in his own voice for the first time” vowed to hit back at Israel if it carries out further airstrikes, and “signaled that he may let terror groups open a front against Israel across the Golan Heights border,” Ya’ari said.

With Hezbollah and Iran providing “massive aid” to Assad in his war against the rebels trying to oust him, he is under pressure to ensure Hezbollah, in return, gets the sophisticated weapons it wants from Iran. Israel twice this month struck targets around Damascus where a shipment of sophisticated Iranian Fateh-110 missiles were being held en route to Damascus.

Last week, National Security Adviser Yaakov Amidror told a gathering of European Union ambassadors that while Israel may not be able to prevent the delivery of S-300 batteries to Syria, it would act to prevent them from becoming operational.

During the closed-door briefing, which was attended by 27 diplomats, Amidror made it clear that even though Israel was determined to prevent the Syrians from deploying the missiles, it would not necessarily launch a military strike to destroy them, diplomats that were present at the meeting said according to Hebrew media reports.

Amidror explained that while Russia was dead set on supplying the system, it was unclear when the batteries would become operational. The national security adviser added that Israel, together with the United States, would continue to act through diplomatic channels to prevent the S-300s from posing a threat. Israel hoped to persuade the Russians to withhold critical parts and training that were need to make the system operational, he said.

Amidror also opined that the main motivation for the Kremlin in providing the missiles was not so much an interest in becoming embroiled in the Israel-Syria standoff, but rather an attempt to engage the West in a game of one-upmanship over its support for rebels fighting the Assad regime, the diplomats said.

In this undated file photo a Russian S-300 anti-aircraft missile system is on display in an undisclosed location in Russia (photo credit: AP)

In this undated file photo a Russian S-300 anti-aircraft missile system is on display in an undisclosed location in Russia (photo credit: AP)

The Syrian president told Al-Manar that his country would retaliate for any future Israeli attack on Syria, and said he would not “get in the way” of any Syrian groups that attempted to liberate the Golan Heights, which Israel captured during the 1967 Six Day War, Al Akhbar reported. He spoke of “public pressure” to open the Golan front.

The sophisticated S-300 air defense system, considered one of the most advanced in the world, takes about four months to become operational and would require intensive training, including calibration that can only be carried out on-site in Syria, experts say.

Prime Minister Benjamin Netanyahu met with Russian President Vladimir Putin earlier in May seeking to dissuade him from going ahead with the deal but, according to Haaretz, has since admitted to various European foreign ministers that his mission had failed and the deal would go ahead.

Israeli media reports said Netanyahu had warned Putin of a descent into war should Russia make the delivery. Netanyahu said that if acquired by Assad, the S-300 “is likely to draw us into a response, and could send the region deteriorating into war,” Channel 2 reported.

On Thursday, Strategic Affairs Minister Yuval Steinitz met with the Russian ambassador to Israel, Sergey Yakovlev, and the two agreed to stay in touch.

The missile deal has ratcheted up tensions between Jerusalem and Damascus, which were already high following the two airstrikes in early May.

Russian President Vladimir Putin, right, listens to Israeli Prime Minister Benjamin Netanyahu during their meeting at the Bocharov Ruchei residence in the Black Sea resort of Sochi, Russia, Tuesday, May 14, 2013. (photo credit: AP/ Maxim Shipenkov)

Russian President Vladimir Putin, right, listens to Israeli Prime Minister Benjamin Netanyahu during their meeting at the Bocharov Ruchei residence in the Black Sea resort of Sochi, Russia, Tuesday, May 14, 2013. (photo credit: AP/ Maxim Shipenkov)

Aside from the unique strategic capacities that the S-300 air defense missiles would afford Syria, putting planes taking off from central Israel and its main international airport within the missiles’ range, Jerusalem also fears that the system could fall into the hands of terror groups like Hezbollah, which has become increasingly involved in fighting the Syrian rebels.

On Wednesday, Syrian Foreign Minister Walid al-Moallem warned that Syria would “retaliate immediately” if Israel strikes on Syrian soil again.

“We’ve declared to the world that we will retaliate immediately if Israel attacks again,” Moallem said in an interview with the Lebanese TV station Al-Mayadeen. ”Any aggression will be met with a response of a similar magnitude.”

On Tuesday night, the Russian ambassador to the United Nations said that the sale of the weapons was not the start of an arms race and recommended Israel stay calm over the deal.

In an interview with CNN, Vitaly Churkin suggested that Israel consider the risks involved in taking action against the missile delivery.

“The Israelis will keep a cool head and refrain from reckless actions,” he said, asserting that in the past Russia had responded to Israeli concerns about advanced weapons shipments falling into the wrong hands by guaranteeing that the arms would only go to their intended destinations.