“It’s certainly another page of the story,” Augustus Richard Norton, a professor of international relations at Boston University and an expert on Middle East political history, said of the French announcement. “I think it’s important. But it will be much more important if other countries follow suit. I don’t think we’re quite there yet.”

Some drew an analogy to France’s leading role in the early days of the Libyan uprising when it helped funnel aid, and later military support, to the rebels who had firmly established themselves in eastern Libya and would later topple Col. Muammar el-Qaddafi. But in Syria, rebels have not been as organized and have no hold on significant amounts of territory — at least not enough to create a provisional government that could resist Mr. Assad’s military assaults. The West has also refused, so far, to impose a no-fly zone over Syria, which was critical to the success of the Libyan uprising.

Andrew J. Tabler, a Syria expert at the Washington Institute for Near East Policy, said that the new coalition would have to create a secure zone in Syria to be successful, and that that step would require support from the United States, which was instrumental in the negotiations that led to the group’s creation but has not yet committed to giving it full recognition.

What the French have done, Mr. Tabler said, is significant because they have started the process of broader recognition, putting pressure on the group to succeed. “They’ve decided to back this umbrella organization and hope that it has some kind of political legitimacy and keep it from going to extremists,” he said. “It’s a gamble. The gamble is that it will stiffen the backs of the opposition.”

France’s statement also was a clear reflection of frustration with the growing death toll and military stalemate in Syria. It came a week after the re-election of President Obama, who had clearly been unwilling to consider any military policy that could hurt his prospects.

Mr. Hollande’s announcement came as the rebel coalition’s newly chosen leader, Sheik Ahmed Moaz al-Khatib, a former imam of the historic Umayyad Mosque in Damascus and a respected figure in Syria, made a broad appeal to Western and Arab countries for recognition and military aid. Foreign ministers of the Arab League, while approving the new group as the “legitimate representative of the Syrian opposition,” have not agreed on recognizing it as a provisional government to replace Mr. Assad.