Canada, India, Singapore and Egypt are "seriously" interested in buying France's two Mistral warships, a senior French official has said, after Paris scrapped a deal to sell the vessels to Russia over the Ukraine crisis.

Louis Gautier, an official who advises the prime minister on defence and security matters, also told lawmakers this week that the cost of abandoning the agreement with Russia would be at least 1.1 billion euros ($1.2 billion) if the government did not find another buyer, according to a summary of his comments obtained by AFP Friday.

That figure includes the costs of the maintenance required to keep the pair of amphibious helicopter-carriers in operational condition and fees for keeping them docked in the western port of St Nazaire, which together are running at two million euros a month.

However, it does not include the costs of removing Russian fittings -- including communications equipment -- that are already on the ships, Gautier said.

Work to remove the fittings is not expected to be complete until March.

The deal to sell the warships to Russia was formally cancelled in early August in response to Russia's actions in Ukraine.

The French National Assembly will on Thursday debate a bill enshrining the agreement between Paris and Moscow to abandon the deal.

The bill allows France to find another foreign buyer for the vessels, as long as it lets Russia know in writing beforehand.

A diplomatic source, who did not wish to be named, told AFP that meant that "France commits to not sell the Mistrals to a country that goes against Russia's interests".

"In other words, there's no question of selling them to Poland or the Baltic states," the source added.