Novak Djokovic and Juan Martin del Potro will have to complete their Rome Masters quarterfinal on Saturday after torrential rain and lightning forced a suspension on Friday.

Four-time Djokovic was leading 6-1, 1-2 when play was halted for the night.

"We officially announce that due to the heavy rain, the match between #Djokovic and #DelPotro will resume tomorrow. Time TBD," said a statement on the tournament's Twitter account.

The winner will face Dominic Thiem, who knocked out Rafael Nadal, in the semifinals which will also be played Saturday.