BRUSSELS, June 9 -- The number that matters in Tuesday's announcement is not the package count. It is 51.

European Commission President Ursula von der Leyen, presenting the 21st round of EU sanctions against Russia at a press conference in Brussels, confirmed the bloc is proposing to extend transaction bans to 31 additional Russian banks and simultaneously designate 20 banks, cryptocurrency firms, and oil traders based in third countries outside the European Union. Taken together, those 51 entities represent the largest single-day expansion of EU financial transaction bans in the four-year history of the Russia sanctions program.

"We are expanding our transaction bans to 31 more Russian banks and to 20 banks, crypto firms or platforms a...