Washington (AFP) – US officials on Thursday voiced concern at the sale of French warships to Moscow as they mull tougher sanctions on Russia for the political upheaval triggered by the crisis in Ukraine.

“We have regularly and consistently expressed our concerns about this sale even before we had the latest Russian actions and we will continue to do so,” Assistant Secretary for Europe Victoria Nuland told US lawmakers ahead of a visit next week to Washington by French Foreign Minister Laurent Fabius.

The first of two Mistral warships is not due to be delivered to Russia until October, and France has so far resisted pressure to suspend the controversial $1.2 billion contract.

The Mistral is an advanced helicopter assault ship and France’s 2011 agreement to sell them to Russia already triggered protests from the United States and other NATO allies.

The first of the warships, named the Vladivostok, is due to be delivered in October, while the second, “The Sebastopol” is to be delivered in 2015 and stationed with the Russian Black Sea Fleet in the Crimea — annexed in March by Moscow.

French Defense Minister Jean-Yves Le Drian said in March that “the question” of whether to suspend the sale “will arise in October” and any decision was postponed until then.

The United States and its EU allies are mulling whether to impose deeper sectoral sanctions on Moscow for its annexation of Ukraine’s southern Crimea peninsula and its interference in eastern Ukraine.

Fabius is expected to come under pressure from US officials during his visit to Washington next week. He said in late March that Paris may cancel the Mistral sale if Moscow does not change its policies towards Kiev.