EU foreign ministers meeting to find a common response to the mounting crisis in Ukraine were to consider what measures to take in the event of "further possible negative actions by Russia," according to a draft of the final statement seen by AFP.
"In the absence of an agreed solution, the EU will consider/begin preparations for future targeted measures, including an arms embargo," it said.
This section of the draft was in brackets, meaning it is open to change or even removal at the meeting.
The first warship was floated out late last year and is set to be delivered to the Russian navy in October, with the second still under construction.
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Of the 28 EU member states, France and Germany have both pressed the case for dialogue and mediation with Moscow first, downplaying any possibility of sanctions at this stage.
Dutch Foreign Minister Frans Timmermans told reporters on arriving for the meeting that "sanctions are not in order today but sanctions will become inevitable" if there is no change in Russia's position.
"The European Union strongly condemns" Russian actions in Ukraine, especially its de facto occupation of Crimea, largely pro-Russian and home to its key Black Sea fleet.