Ukraine's match with France was postponed for an hour amid torrential rain Donetsk.
The downpour occurred five minutes into play and will not be resumed before 6pm UK time.
UEFA rules dictate that the match must be played to a conclusion, in full, and if the game is abandoned then it will be rescheduled for the following day.
Rule10.08 states: "If a match cannot commence or is abandoned before the end of normal playing time or during any extra time because the field is not fit for play or for other reasons, it must be played or replayed in full the next day.
"If, for reasons beyond control, the match cannot be replayed the next day, the UEFA administration will take a final decision."