Paris: Working with the Syrian army to fight the Islamic State group is not on the cards until President Bashar al-Assad has been removed from power, French Foreign Minister Laurent Fabius said on Monday.
France's top diplomat said it was "obvious" Assad could not work alongside moderate rebels in Syria.
"If we achieve a political transition and it's no longer Bashar in charge of the Syrian army, there could be joint actions against terrorism. But under Bashar it's not possible," Fabius told France Inter radio, speaking at the UN climate conference just outside Paris.
"It is obvious that it's not under the leadership of Mr Assad that the army could be engaged alongside the moderate opposition," he added.
France has demanded the removal of Assad, describing him as a "butcher" of his own people.
But there had been signs it might moderate its position towards Assad as its priority shifted to tackling the Islamic State group which carried out the Paris attacks earlier this month.
Fabius fuelled the rumours, by telling France's RTL radio last week that "regime forces" could potentially join the fight against IS.
His comments made headlines around the world, even after Fabius said he was merely referring to a post-Assad regime.
Syrian Foreign Minister Walid Muallem seized on Fabius' proposal, saying it was "better late than never".
Germany backed Fabius's calls over the weekend, with Defence Minister Ursula von der Leyen saying she was open to working with "part of the troops in Syria".
"Like in Iraq, where training of the local troops had been successful," she told public broadcaster ZDF.
However a German government spokeswoman clarified on Monday that Berlin also had no plans to link up with Assad's forces.
"There will be no cooperation with Assad and no cooperation with troops under Assad that is the position of the German government," the spokeswoman, Christiane Wirtz, told a press briefing.
Most analysts believe that Western training of troops in the Middle East has been an abject failure.
"Our track record at building security forces over the past 15 years is miserable," former US ambassador to Afghanistan Karl Eikenberry told the New York Times last month.
The conflict in Syria is likely to feature in many of the meetings organised on the fringes of the climate conference, where 150 world leaders are gathered.
Discussing the possibility of a meeting between Turkish President Recep Tayyip Erdogan and his Russian counterpart Vladimir Putin who are embroiled in a diplomatic spat after Turkey shot down a Russian plane last week Fabius said "if we can facilitate something, we will.”
