Europe’s decision to allow the arming of Syrian rebels and Russia’s renewed pledge to supply Syrian President Bashar Assad’s regime with advanced missiles could transform an already brutal civil war into an East-West proxy fight — although Britain said Tuesday it won’t transfer any weapons to the rebels before diplomacy is given a chance.

The possibility of an arms race in Syria overshadowed attempts by the United States and Russia to bring representatives of the Assad regime and Syria’s political opposition to peace talks at an international conference in Geneva, possibly next month.

The talks, though seen as a long shot, constitute the international community’s only plan for ending the conflict that began more than two years ago and has killed more than 70,000 people.

In Syria, the commander of the main Western-backed umbrella group of rebel brigades said he urgently needs Western anti-tank and anti-aircraft missiles to prevent further regime gains on the battlefield. The rebels’ weapons are no match for the Syrian regime’s modern tanks and warplanes, he said.

“We are very disappointed,” Gen. Salim Idris, military chief of the Free Syrian Army, said of the European Union’s apparent decision not to send weapons, if at all, until after the Geneva conference. “We don’t have any patience (any) more.”

In any case, Europe might think twice about sending such weapons into a chaotic war zone where they could quickly be seized by Islamic militant rebels, some of whom have pledged allegiance to the al-Qaida terror network.

Britain, which along with France had pushed for ending the EU arms embargo, wants to use the threat of arming the rebels as leverage to ensure that Assad negotiates in good faith.

Syria’s fractured opposition, which has not yet committed to the Geneva talks, could also be lured to the table if attendance is linked to receiving weapons in the event that talks fail. Opposition leaders have said they will participate in talks only if Assad’s departure from power tops the agenda, a demand Assad and his Russian backers have rejected.

British Foreign Secretary William Hague said peace talks are a priority and that “as we work for the Geneva conference, we are not taking any decision to send arms to anyone.”

However, Russian Foreign Minister Sergey Lavrov warned that recent actions by the West “willingly or unwillingly are undermining the idea of the conference.” He denounced the lifting of the EU arms embargo as an “illegitimate decision,” saying that supplying weapons to non-governmental groups “goes against all norms of international law.”

At the same time, Lavrov’s deputy affirmed Tuesday that Russia won’t abandon plans to send long-range S-300 air defense missile systems to Syria, despite strong Western and Israeli criticism. It is not clear if Russia has already sent some of the missiles, which would be a major boost for Syria’s air defense capabilities, including against neighboring countries that oppose Assad’s regime.

Britain and Russia traded allegations of hypocrisy over potential weapons shipments.

U.S. State Department spokesman Patrick Ventrell said Washington welcomes the EU decision as a show of support for the Syrian opposition and as a message to the Assad regime that such support will only grow. He said the Obama administration will continue to provide non-lethal assistance to the rebels, and hasn’t made a decision on whether to arm them.

Ventrell condemned Moscow’s decision not to drop plans to sell S-300 missiles to Syria. “We’re talking about a regime that’s willing to go to enormous lengths to use massive force against civilians, including Scud missiles and other types,” he said. “We condemn all support of arms to the regime.”

Further raising the risk of a regional war, Israel warned it would be prepared to attack any such missile shipments. Israeli Defense Minister Moshe Yaalon said Israel believes the Russian missiles have not yet been shipped, but that the Israeli military “will know what to do” if they are delivered.

Earlier this month, Israeli airstrikes hit suspected shipments of advanced Iranian missiles near the Syrian capital of Damascus that were purportedly intended for Assad ally Hezbollah, the Lebanese militia that is fighting alongside Syrian regime forces.

Israel has said it would not hesitate to attack again to disrupt the flow of game-changing weapons threatening its security.