(JTA) — Russia will not sell the S-300 advanced air defense system to Syria, Russian Foreign Minister Sergei Lavrov said.

Lavrov’s statement, published last Friday by the Itar-Tass news agency, came in reaction to the publication of an article two days earlier in The Wall Street Journal reporting that Israel had informed the United States of an imminent deal to sell the advanced ground-to-air missiles.

Possession of S-300 missiles would significantly boost Syria’s ability to stave off intervention in its current civil war, the daily reported.

Lavrov said Russia would fulfill the contracts it has already concluded with Damascus, but they did not include sales of the S-300 system.

Israeli Prime Minister Benjamin Netanyahu is expected to travel to Russia this week to meet with Russian President Vladimir Putin to discuss concerns over planned weapons sales.

U.S. Secretary of State John Kerry on May 9 said the United States does not want Russia to sell weapons to Syria and has opposed transfers of missile systems to the country in the past because of the threat to Israel.

“I think we have made it crystal clear we would prefer that Russia was not supplying assistance,” Kerry said at a news conference after meeting Italian Foreign Minister Emma Bonino.

The government of Syrian President Bashar Assad has been seeking to purchase the advanced S-300 missile batteries, which can intercept manned aircraft and guided missiles, from Moscow for many years.

Western nations repeatedly have urged Russia to block the sale, which they argue could complicate any international intervention in Syria’s escalating civil war.

The Journal said the information provided to Washington by Israel showed that Syria has been making payments on a 2010 agreement with Moscow to buy four batteries for $900 million, including a payment made this year through Russia’s foreign-development bank known as the VEB.

The paper said the package included six launchers and 144 operational missiles, each with a range of 200 miles, with an initial shipment expected in the next three months.