European Commission President Ursula von der Leyen says member states face a "historic decision" at a June 23-24 summit on whether to grant Ukraine membership status.
"I hope that in 20 years, when we look back, we will be able to say that we did the right thing," von der Leyen told journalists on her way back from a visit to Kiev.
The challenge would be to emerge from the EU summit later in June with a unified position "that reflects the scope of this historic decision."
Von der Leyen had travelled to Kiev earlier in the week to discuss with President Volodymyr Zelensky, among other things, remaining points of contention in Ukraine's application for membership.
The EU executive wants to publish its recommendation at the end of the week on whether the country, which has been resisting a Russian invasion since February 24, should be granted EU candidate status.
'Much remains to be done'
Ukraine has achieved a lot in recent years, but much remains to be done, said von der Leyen on her way back to Poland.
"Our recommendation will carefully reflect that," she added.