"Yes, there can be decisions by unanimity on new sanctions coming in the next couple of weeks," Mogherini said at the doorstep of the EU Foreign Affair Council and Competitiveness Council, answering a corresponding question.
The Ukrainian vessels and their crew were detained by Russia after failing to respond to a lawful demand to stop.
Russian President Vladimir Putin said that the incident was a provocation prepared in advance as a pretext to introduce martial law.
Putin suggested that it could be connected with Poroshenko's low approval ratings ahead of the 2019 presidential vote.
Following the incident, Ukrainian President Petro Poroshenko decreed a three-month martial law in several regions of the country neighboring Russia, as well as the coast of the Black Sea and the Sea of Azov.