The Saudi role is indicative of the geopolitical importance of Syria, a neighbor of Israel and a close ally of Iran, Saudi Arabia's fierce rival in the region. Analysts say Saudi officials are keen to see Assad replaced by a government reflecting Syria's majority Sunni population, which would presumably be hostile to Tehran.
Saudi Arabia and its gulf allies, especially oil- and gas-rich Qatar, reportedly pushed for some form of direct aid to the rebels, who are facing off mostly with rifles against Assad's heavily armored military.
"My country cannot take part in any [meeting] that would not lead to protecting the Syrian people," Saudi Foreign Minister Prince Saud al Faisal was quoted as saying, a clear rebuff of an approach that opposition critics call rhetoric over action.
During an appearance with Clinton in Tunis, the foreign minister said that arming the rebels was "an excellent idea."
Casting a shadow over the Tunisia meeting was the specter of neighboring Libya, where a Western-led bombing campaign contributed directly to the ouster last year of Moammar Kadafi.
Neither Russia nor China wants to see a repeat of the Libya scenario in Syria. The two countries have twice vetoed U.N. Security Council resolutions condemning Assad's handling of the Syrian protests.
Neither Russia nor China attended the Tunis conference. Both nations have called for "dialogue" to resolve the Syrian crisis and are opposed to any international steps that could lead to foreign military intervention in Syria, where Russia has considerable business and strategic interests. Russia is also keen not to lose its last major ally in the Arab world.
Clinton denounced the stance taken by Russia and China as "despicable."
Assad did lose one longtime ally. The Palestinian militant group Hamas ditched its longtime patron and publicly backed the opposition. Hamas recently abandoned its former headquarters in Damascus, signaling a shift that was confirmed Friday. Assad still retains the support of militant group Hezbollah, based in Lebanon, which is also a close ally of Iran.
Opposition activists reported that violence continued to rage across much of Syria on Friday. The Local Coordination Committees, an opposition coalition, said at least 103 people died, 32 of them in the central city of Homs, which has been under government shelling for three weeks.
A group of international Red Cross and Syrian Red Crescent ambulances arrived in Homs' hard-hit Baba Amr neighborhood Friday to begin evacuating civilians, a Red Cross spokesman said. Among the injured were two Western journalists hit in shelling Wednesday that killed two other journalists: veteran U.S.-born reporter Marie Colvin of London's Sunday Times and French freelance photographer Remi Ochlik.
Times staff writer Paul Richter in Washington contributed to this report.