BRUSSELS—The European Union is set to roll over until March 15 sanctions targeted against almost 200 Russian and Ukrainian-separatist individuals and firms to maintain pressure on Moscow to fully implement the Minsk ceasefire terms by the end of the year, diplomats said.

The decision is expected to be made at a meeting of senior EU officials on Wednesday and should be signed off by ministers in mid-September, the diplomats said. The asset freeze and travel bans were due to expire Sept. 15.

The...