Israel warned it “will know what to do” if Russia delivers promised anti-aircraft missiles to its war-torn ally Syria, amid growing fears of a wider conflict brewing as the fighting spills into Lebanon.

Newmedai / AFP / MESOP  – 29.5.2013 – Israel said Tuesday it would act if the Russian delivery went ahead, while Syria’s top rebel commander gave Hezbollah, the powerful Lebanese Shiite movement, a 24-hour ultimatum to stop fighting alongside regime forces.

The developments stoked tensions after the European Union decided to lift an embargo on supplying weapons to Syria’s rebels, in a move the opposition reacted to with caution. Syria’s regime joined its ally Russia in condemning the EU decision as an “obstruction” to peace efforts, while accusing the bloc of supporting and encouraging “terrorists.”

The United States said it supported the EU move as a show of “full support” for the rebels, despite its own refusal to provide arms it fears will end up in jihadist hands. The lifting of the embargo “sends a message to the Assad regime that support for the opposition is only going to increase”, said US State Department spokesperson Patrick Ventrell. Moscow said its planned to deliver to Damascus the S-300 missiles — designed to intercept aircraft or other missiles like Patriots NATO has already deployed on Turkey’s border with Syria — which were part of existing contracts. “We consider these supplies a stabilizing factor,” deputy foreign minister Sergei Ryabkov said, adding they could act as a deterrent against foreign intervention.  Israel has strongly objected to the delivery, and its defense minister warned of a response. “The deliveries have not taken place, and I hope they do not. But if, by misfortune, they arrive in Syria, we will know what to do,” said Moshe Yaalon.

The Jewish state has reportedly carried out at least three strikes against Syria since the uprising against President Bashar al-Assad erupted in March 2011, apparently targeting weapons. On the ground, the conflict has already spilled over into Lebanon, and in the latest incident three soldiers were killed in an attack near the northern border town of Arsal, where most people back the uprising in Syria. And in the eastern Lebanese town of Hermel, security sources said six rockets apparently fired from Syria hit the Hezbollah stronghold, wounding seven people.Hezbollah is allied with Syria’s regime and fighting alongside the army against the rebels, including in the central town of Qusayr, where it has lost dozens of men.