Djokovic set up the meeting with a straight-sets victory over Tomas Berdych this afternoon, while earlier in the day Del Potro had shaken off an injury to beat fourth seed David Ferrer, also in straight sets.
Djokovic will go into the match as the heavy favourite to progress, but he is refusing to take the 2009 US Open champion lightly.
"He is a great player. I have a great respect for him," Djokovic is quoted as saying by PA Sport.
"He's a Grand Slam winner. He has struggled with injuries in the last few years, but every time he comes back he comes back very strong because he just has this talent and quality.
"It's the semi-finals, so everything is on the table. We both want to win."
Djokovic is still yet to drop a set during this year's tournament.