"The fight against Daesh is crucial, but it will only be totally effective if all the Syrian and regional forces are united," Fabius told the French regional newspaper Le Progres on Saturday.
A united Syria implies keeping the current government intact, and ultimately Bashar al-Assad in power.
"A united Syria implies a political transition. That does not mean that Bashar al-Assad must leave even before the transition, but there must be assurances for the future".
Fabius' comments mark a softening of France's position on the Syrian president, long perceived as a pariah by Western countries.
Up until now, Paris, along with Washington, has insisted that Assad--described as a "butcher"--must step down as part of any political solution to the four-year conflict.
That position has now softened in the wake of the deadly Paris attacks staged by Islamic State militants. France's focus has shifted to tackling Islamic State and less on ending the Syrian conflict.
In terms of the transition process, Fabius admitted earlier this week it was "obvious" Assad could not work alongside moderate rebels.
The transition for now however, is not the priority.