"We have to go to Raqqa ... it will automatically be local forces that will liberate Raqqa even if French forces, USA forces, the coalition contribute with air strikes to dismantle Daesh", Le Drian told Europe 1 radio, using an Arabic acronym for ISIS.
The Syria Democratic Forces, a Kurdish-led group that includes Arab fighters and is backed by USA air power, announced the offensive earlier on Sunday.
Raqqa, seized by ISIS in January 2014, became its de facto capital in Syria and a magnet for foreign fighters.
If Mosul is any indication, the battle for Raqqa will be a long and grinding one.
A senior US official says Washington will provide air support for an offensive to retake the Syrian city of Raqqa, the de facto capital of the Islamic State group.
The SDF alliance also includes the Kurdish YPG, which Turkey considers a terrorist group.
As the Raqqa offensive began, Turkish-sponsored groups were preparing to intervene by moving against Islamic State-held al-Bab, a strategic Syrian town 30km south of the Turkish border. This would force the Kurds to stop their campaign toward Raqqa to protect their areas, he said.
The Kurdish-Arab force leading the fight to take the Syrian city of Raqa from the control of Islamic State jihadists had said earlier that Washington had agreed Turkey would play no role in the offensive.
Fallon also said United Kingdom strikes are "making a difference" in the sustained assault against IS in the northern Iraqi city of Mosul, where Iraqi forces launched a major operation last month to drive out the extremists.
The brutality of life in the city has been documented by a secret group of activists called Raqqa Is Being Slaughtered Silently.
This frame grab from video provided by Arab 24 network, shows officials with the US -backed Syria Democratic Forces at a press conference in Ein Issa in northern Syria.
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"We know this plot-and-planning is emanating from Raqqa".
He said that as in the Iraqi city of Mosul, the target of another anti-IS offensive, "the fight will not be easy and there is hard work ahead". Over the summer, Turkish forces intervened in northern Syria, targeting Islamic State militants but also acting as a curb to Kurdish territorial ambitions in the country.
Turkey has lobbied to be part of the operation in place of the Kurdish fighters."The Kurdish-led rebels say the operation, including Arab and Syrian Turkmen fighters, will start in the countryside outside Raqqa and move toward the city".
The SDF, meanwhile, urged the regional and worldwide powers that have been affected by the IS to take part in the "honor to eliminate the core of the global terrorism" represented by the IS by providing all kinds of support to the SDF.
Given its importance in ISIS' infrastructure, the city has often been the target of coalition airstrikes targeting key ISIS facilities and multiple ISIS leaders, including Jihadi John, who was killed by a drone strike in November 2015, according to USA officials. The Observatory also said IS detonated two auto bombs targeting the advancing forces. Because of that, it appears that Syrian Arab groups in the Syrian Democratic Force will make up the main force attacking Raqqa.
Announcing the start of the offensive, the SDF said it hoped Turkey would not get involved in operations within Syria.
No precise timetable for the beginning of the assault on Raqqa itself has been given, but the SDF has asked civilians in the mostly Arab city to avoid areas where ISIS fighters are present or to evacuate from ISIS-controlled territory altogether.
But one of the operation's goals is also to check the advance of Syria's Kurds, and Turkish forces have carried out air strikes against YPG positions. It said more than 25 children were wounded in addition to the six killed.
The announcement by the Syria Democratic Forces was made Sunday at a press conference in Ein Issa, north of Raqqa.
Unlike several successful military efforts to drive Islamic State militants out of cities in Iraq, the Raqqa offensive faces several political obstacles and is likely to be much more complex.
Dominated by the powerful Kurdish People's Protection Units (YPG), the SDF has in recent months flushed IS out of swaths of territory in northern Syria, including the flashpoint town of Manbij in August.