"If we require, even before negotiations start, that Assad step down, we won't get far," Fabius was quoted in Le Figaro as saying in a preview of the French daily's edition on Tuesday.
The comments represent a softening of France's position towards Assad, whose four-year war against rebel groups and Islamic State fighters has claimed more than 200,000 lives.
The United States and Britain have already made similar shifts to their stances on Syria, as Russia bolsters its support for Assad with a military build-up in the country.
US Secretary of State John Kerry said on Saturday that the timing of Assad's exit following a peace deal would be negotiable.
France believes a diplomatic resolution would require the establishment of a government of national unity including elements of Assad's administration "to avoid the kind of collapse seen in Iraq", Fabius said in the interview.
