Some 400 Russian sailors are returning home, French shipbuilder DCNS said Wednesday, as Paris weighs whether to deliver the Mistral-class warship to Russia amid the Ukraine crisis.

"I can confirm that the Russian sailors will return (to Russia) before the end of year," said a DCNS spokesman.

The spokesman did not give a date of departure and could not say whether they would return for more training on the high-tech vessel.

According to the Ouest-France local paper, the sailors' departure is "definitive" and sources said they could leave as early as Thursday morning.

Last month, French President Francois Hollande pushed back "until further notice" the delivery of the first of two Mistral-class warships Russia has ordered from France.

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.

But amid the Ukraine conflict and the rapid decline in the West's relations with Russia, France has come under intense pressure from its allies, particularly the United States, and in September postponed the delivery.

Paris faces a serious dilemma over the Mistrals.

It could be liable for hefty fines if it breaches the 1.2-billion-euro ($1.5-billion) contract.

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.