A day after securing an end to the European Union’s weapons embargo on Syria, Britain and France are facing criticism from Russia and pressure at home and abroad to show restraint before acting to arm the rebels seeking to oust Syrian ­President Bashar al-Assad.

Britain, along with France, scored a diplomatic victory in Paris on Monday, effectively blocking an attempt by other European nations to extend the regional embargo that has prevented them from sending weapons to help the Syrian opposition. Britain said it has no immediate intention to ship arms, and in Paris and London, Monday’s decision was portrayed as a tool aimed at pressuring Assad to negotiate an end to the conflict.

But the decision has opened a possible route for Britain and France, which have been leading the charge in the West for more support to the Syrian opposition, to act unilaterally should they choose to do so.

After the French intervention in Mali in January, Monday’s move once again underscored the inability of the E.U. to forge a united front on major foreign policy issues. It was bitterly opposed by a number of European countries, including Austria. They fear that any arms sent to the rebels could fall into the hands of Islamist extremists within the opposition and lead to more regional spillover of the conflict.

“We are a peace community, and we would like to stay as a peace community,” Austrian Foreign Minister Michael Spindelegger told journalists in Paris. Spindelegger said Britain and France have agreed not to deliver any weapons until at least August, to give more time to international attempts at brokering a peace deal.

Interactive Grid: Keeping track of the conflict in Syria through videos, images and tweets.

In Washington, Obama administration officials voiced strong support for letting the embargo lapse, saying its end would contribute to the two-track policy pursued by supporters of the Syrian opposition: backing the rebels while pushing for a political settlement.

“We welcome the E.U. action,” White House spokesman Jay Carney said.

At the same time, Carney and others said the administration opposes Russian shipments of arms, including sophisticated S-300 air defense systems, to the Assad regime.

“We condemn all support of arms to the regime,” said State Department spokesman Patrick Ventrell. “We’ve seen how the regime uses those arms. When we’re talking about the opposition, that’s a different group. And, clearly, they are the people who are defending themselves in the face of an enormous onslaught and a despicable onslaught of violence against themselves.”

Criticism from Russia

Russia denounced the E.U. action, saying it placed Europeans on the brink of supplying arms to a murky rebel force.

“You cannot declare the wish to stop the bloodshed on one hand and continue to pump armaments into Syria on the other hand,” Sergei Ryabkov, the deputy foreign minister, said Tuesday at a news conference in Moscow.

In a commentary posted on the Russian Foreign Ministry Web site, spokesman Alexander Lukashevich said Moscow is concerned that the E.U. decision might persuade Syrian rebel groups not to join a peace conference, led by Russia and the United States, that is tentatively planned for next month.

Russian Foreign Minister Sergei Lavrov later took that thought a step further in comments to reporters, suggesting that certain “Western partners, including the U.S. and France,” may be seeking to undermine the conference.

At the same time, Russia defended its decision to continue supplying air defense and anti-ship missiles to the Syrian government in accordance with previously signed contracts.

“The Russian Federation is supplying arms to legitimate authorities,” Ryabkov said. “This is not an abstract or idle argument about who these authorities are and why they have the right to receive armaments of this or that sort and the other side has no such rights.”

Moscow’s envoy to NATO, Alexander Grushko, told journalists that Russia will continue to honor its commitments to deliver S-300 missile systems to Damascus. “We will fulfill the signed contracts,” Grushko said. “Russia has been acting in total compliance with international law.”

‘Too little, too late’

Louay Safi, a spokesman for the Syrian Opposition Coalition, described the E.U. decision as a “positive step.” But he added that arms needed to be sent immediately, citing the increasing threat to the rebels posed by the Lebanese Shiite movement Hezbollah, which is backed by Iran and has allied itself with Assad.

“We are afraid that this may be too little, too late,” Safi said in a telephone interview. “Syria is now being attacked by Hezbollah in Qusair and the suburbs of Damascus. If the Free Syrian Army is not given the heavy weapons it needs immediately, we think Syria will be lost to Iran and Hezbollah. The West will have to bear the results of that.”

The two-year-old conflict has morphed into a complex, multifaceted war that is increasingly destabilizing Syria’s neighbors. Three Lebanese soldiers were fatally shot in the border town of Aarsal on Tuesday, a day after two rockets struck a Hezbollah stronghold in southern Beirut, injuring four.

In Britain, the Conservative-led government of Prime Minister ­David Cameron is facing considerable domestic pressure to show restraint. Analysts said domestic opposition might impede any move by Britain to ship arms to the Syrian opposition, if and when London opts to do so.

“Many Conservative MPs are against us supplying arms to Syria once the embargo is lifted,” John Redwood, a member of Parliament and chairman of the Conservative Party’s Economic Affairs Committee, said in a statement on his Web site. “Our advice to the Foreign Secretary is simple — do not use this new U.K. authority.”

The opposition Labor Party echoed the concerns. “Syria is awash with arms, so to whom would weapons be supplied?” shadow foreign minister Douglas Alexander told the BBC early Tuesday. “How would the U.K. government prevent British-supplied weapons falling into the wrong hands?”

Valentina Soria, a security analyst at IHS Jane’s Terrorism and Insurgency Center in London, said Cameron’s government would need “at least a minimum of domestic political consensus” before acting to arm the rebels.

“And there are clearly some who are more reluctant to see the government act,” Soria said.

Still, Foreign Secretary William Hague hailed Monday’s decision as a significant step toward forcing Assad to more seriously negotiate an end to the conflict.

“This does not mean that we have made any decision as the United Kingdom to send arms to the National Coalition, but we now have the flexibility to respond in the future if the situation continues to deteriorate and if the Assad regime refuses to negotiate,” Hague said in a statement.

Loveday Morris in Beirut, Will Englund in Moscow and Karen DeYoung in Washington contributed to this report.