The Syrian President has threatened Israel with renewed fighting in the Golan Heights.

In an interview Bashar al-Assad has also said Russia is committed to supplying him with weapons.

Washington warned that any such weapon deliveries from Moscow would only prolong the conflict in which an estimated 94,000 people have died March 2011.

A senior European Union aide said Mr. Assad's comments and the reluctance of the opposition to attend Geneva were part of a "normal escalation" as both sides jockey to arrive at a peace conference with the upper hand.

Mr. Assad also accused Israel of supporting Syrian rebels. "Israel's involvement with the terrorists or its support for the terrorists aims to achieve two things," Mr. Assad said. "First, strangling the resistance [Hezbollah], and second, striking Syria's air defenses."

Israel has conducted a series of airstrikes near the Syrian capital Damascus—the latest in early May—targeting what U.S. officials said were shipments of Iranian-made rockets bound for Hezbollah in Lebanon.

Israel hinted this week that it would take further action if Syria receives advanced antiaircraft rockets from Russia. The Russian systems would pose further threats to Israel and make it more difficult for Western countries to impose a no-fly zone to protect opposition-held areas across Syria.