Russian Foreign Minister Sergei Lavrov on Friday warned France its reputation was on the line over the delivery of a controversial warship to Russia, which has been delayed due to the conflict in Ukraine.

His comments came as Paris warned the two Mistral-class helicopter carriers it built for Russia may never be delivered, with a lasting ceasefire in war-torn eastern Ukraine so far proving elusive.

"I am a little fed up with this question. It is not our problem anymore, it is a problem of France's reputation. They have to fulfil all the obligations under the contract," Lavrov told journalists on the sidelines of an OSCE ministerial conference in Switzerland.

French President Francois Hollande last week again delayed "until further notice" the delivery of the first warship, a vast grey vessel named Vladivostok which is currently anchored off western France.

He said the "current situation in eastern Ukraine still does not allow for the delivery."

Defence Minister Jean-Yves Le Drian said Friday that Paris had not budged on its decision, even as warring parties announced a fresh truce from December 9.

"For the moment we are not delivering. We may never deliver. The Russians need to realise this situation," he said.

The final date for delivery has not been announced, but Hollande has insisted he will not give in to pressure and the contract has not yet been broken.

Moscow's ambassador to France Alexandre Orlov said that if France did not want to deliver the ships, it should pay Russia back.

"The deadline in the contract has not yet expired," he told Europe 1 radio. "The Mistral contract is a commercial contract, there are commitments from one party to pay and the other party to deliver. If one party does not want to deliver the merchandise it must reimburse" the other.

The first of the two assault ships -- which can carry 16 helicopters, four landing crafts, 13 tanks, 450 soldiers and a hospital -- was supposed to be delivered in November, according to the original deal signed in 2011.

- A French dilemma -

The Mistrals have placed France in a sticky situation.

If it breaches the 1.2-billion-euro ($1.5-billion) contract with Russia it faces hefty fines.

But it would also risk the wrath of its allies around the world if it were to deliver the hot-button technology to Russia at a time when Moscow is in the diplomatic deep-freeze over the Ukraine unrest.

With a flatlining economy France could find itself saddled with two massive warships equipped with Russian technology that it cannot sell to another client and no money to show for it.

Also weighing on the French decision is its reliability as an arms export partner as it seeks to break into the international market with its Rafale fighter jets.

Le Drian said Friday he was optimistic about negotiations to sell 126 Rafale jets to India in a contract worth 12 billion dollars.

Hollande has repeatedly said the ceasefire in Ukraine must be fully respected before the first ship can be handed over, however fighting has shattered all truce deals to date in a conflict that has left 4,300 dead in eight months.

Russia has repeatedly denied accusations from the West that it is arming and supporting the rebels in eastern Ukraine.

Lavrov said he was hopeful a ceasefire would hold.

"It is a very difficult situation but I hope parties have come close to conclude a final agreement," he told journalists in Basel, Switzerland.