But more than a year into the Syrian revolt, the opposition is still hobbled by the infighting and fractiousness that have prevented the movement from gaining the kind of political traction it needs to present a credible alternative to Assad.
"There is an opportunity before the conference of Syrian opposition today that must be seized, and I say and repeat that this opportunity must not be wasted under any circumstance," Arab League chief Nabil Elaraby told nearly 250 members of the Syrian opposition at the opening of the two-day conference in Cairo.
"The sacrifices of the Syrian people are bigger than us and more valuable than any narrow differences or factional disputes," he said.
Nasser al-Kidwa, deputy to U.N. special envoy Kofi Annan, said that unity of purpose and vision was "not an option, but a necessity if the opposition wants to bolster its popular support and trust and increase international support."
The divisions are tied to issues at the heart of the revolution: Whether to seek dialogue with the regime, whether outside military intervention is needed, and what ideology should guide a post-Assad Syria.
Unlike Libya's National Transitional Council, which brought together most factions fighting Moammar Gadhafi's regime and was quickly recognized by much of the international community, Syria's opposition has no leadership on the ground.
Regime opponents inside and outside Syria are a diverse group, representing the country's ideological, sectarian, and generational divides. They include dissidents who spent years in prison, tech-savvy activists in their 20s, and former Marxists and Islamists.
Communication between those abroad and those in the country is extremely difficult. Political activists in Syria are routinely rounded up and imprisoned. Many are in hiding, communicating only through Skype using fake names, and the country is largely sealed off to exiled dissidents and foreign journalists.
The Cairo conference brought together various opposition groups - including the Syrian National Council and the National Coordination Body for Democratic Change in Syria - to try to agree on a united front to represent them, as well as to work out a transition plan for how to end to the conflict.
However, the main rebel group fighting Syrian government forces on the ground, the Free Syrian Army, was not represented at the talks. Faiz Amru, a member of the Joint Military Command, which is affiliated with the FSA, said the Cairo meeting was purely political, so rebels were not invited.
Besides the conference in Cairo, opposition members plan to meet Russian officials later this month, a Russian news agency reported. The Moscow talks are significant because the Kremlin is Syria's most important ally, protector and supplier of arms.
Diplomatic hopes have rested on persuading Russia to agree to a plan that would end the Assad family dynasty, which has ruled Syria for more than four decades.
Moscow's determination to preserve its last remaining ally in the Middle East has blocked efforts by the United States and other Western powers to force Assad out.