updated 04/27/2011 AT 1:00 PM ET
•originally published 04/27/2011 AT 2:15 PM ET
Justin Timberlake plays a guy in a casual relationship with his friend in the new movie Friends with Benefits – but the singer-actor isn’t such a fan of casual hookups in real life.
“It’s a really good idea until it becomes a bad idea,” Timberlake tells Ellen DeGeneres in an interview with his costar Mila Kunis scheduled to air Thursday. “It probably becomes a bad idea really fast.”
Timberlake, 30, who recently split from longtime girlfriend Jessica Biel and subsequently denied any romantic relationship with Kunis, says it’s hard to keep emotions from interfering – especially when sex is involved.