Polish Foreign Minister Radoslaw Sikorski has urged France to pull the plug on a 1.2-billion-euro deal to sell two warships to Russia due to the Ukraine crisis, according to sn interview published Tuesday.

Russia would use the two Mistral-class helicopter carriers to threaten its Black Sea neighbours, Sikorski told French newspaper Le Monde.

France agreed to sell the warships to Russia under a 2011 contract worth 1.2 billion euros ($1.6 billion), with the first due in October and the second in 2015.

Other allies have expressed concern over the deal, including the United States, which said last month that it was not an appropriate time to move forward on such military sales given Russia's actions in the region, including the annexation of Crimea.

Reacting to Sikorski's comments, French foreign ministry spokesman Romain Nadal told reporters that "a contract was signed. It must be honoured".

French President Francois Hollande for his part said last month the sale would continue "for now".

The Mistral, the second-largest ship in the French navy, is a high-seas military base that can transport up to 16 helicopters, four landing craft, 60 armed vehicles and some 700 troops.