French Prime Minister Manuel Valls said on Thursday that conditions have not yet been met for France to deliver two Mistral-class warships to Russia.

"Today the conditions have not been met for their (warships) delivery to Russia," Valls told reporters in the Serbian capital. Paris has been facing mounting pressure to scrap the 1.2 billion euro ($1.5 billion) deal with Moscow over Russia's role in the Ukrainian crisis.

Until the deadly crisis erupted this year the contract to build and sell two mammoth Mistral-class assault ships to the Russian navy had been firmly on track.

But after fierce criticism from its allies France in September postponed the decision to deliver the first ship to Russia.

A ceasefire signed by Kiev and pro-Russia separatists in eastern Ukraine seemed to pave the way for the deal.

But leadership elections held by rebels last weekend threaten to close the lid on any immediate resolution of the crisis.

As a deadline for the controversial delivery of the first ship to Russia nears, France faces a gruelling dilemma: ditch the deal, lose billions and antagonise Moscow -- or go ahead and attract NATO's wrath.

If Paris decides to deliver the amphibious assault ships, which can carry 16 helicopters, four landing crafts, 13 tanks, 450 soldiers and a hospital, it will anger Poland and the Baltic states -- all of which are nervous about the close proximity of an unpredictable Russia.

The United States is also firmly opposed to the delivery.

But if France cancels the deal altogether -- the second ship is due to be delivered some time next year -- it risks potential job losses and fines for not honouring the contract.