An article attributed to Jarba on the website of French newspaper Le Monde said: "Nothing and no one was able -- or willing -- to save the Syrian people, either from Assad's missiles and bombs, or from torture and death in his dungeons, or from suffocation and asphyxiation by chemical weapons."
Despite the loss of 146,000 lives and the millions displaced, Jarba said Assad had "failed to crush the revolution" and "would never succeed".
"The time has come for the free world to help the Syrians to escape their isolation. They should provide the means to fight Bashar al-Assad, and the jihadists that he has done so much to attract."
However, an English-language version of the article released the previous day, made no direct request for military support, a possible reflection of France's greater willingness to engage in military operations in recent years.
France has intervened in Mali and Central African Republic in the past year, and supported direct strikes in Syria last summer following reports that Assad had used chemical weapons.