French President Nicolas Sarkozy, flanked by British Prime Minister David Cameron, urged Syrian opponents of President Bashar Al-Assad Friday to unite so that the outside world could help them overthrow him. Their statement came as Syrian forces unleashed their heaviest pounding of Homs in two weeks after the UN General Assembly overwhelmingly backed an Arab initiative calling on Assad to stand down. Rockets crashed into Khaldiyeh and Bayyada, strongholds of resistance in the central protest hub, at the rate of four a minute, according to one opposition activist inside the beleaguered city. Sarkozy said the lack of unity among opposition groups was as much of a hurdle to resolving the crisis than opposition within the UN Security Council to taking action and warned that without a credible alternative the uprising would fail. “The principle obstacle ... is not just the blockage at the UN. In Libya we couldn't have had the revolution without the Libyans and we won't be able to have a Syrian revolution without the Syrian opposition making enough effort to unite that we can support them more,” Sarkozy said. On Thursday, 137 states voted in favor, 12 voted against and 17 abstained at the UN General Assembly on a resolution endorsing an Arab League plan telling Assad to step down. Russia and China voted against, after vetoing a similar Security Council text on Feb. 4. World powers will meet in Tunisia next week to discuss the crisis.