THE first night of real com petition on “American Idol” was interrupted last night by a taunting confrontation between host Ryan Seacrest and judge Simon Cowell.

“I think you two need to talk after class,” judge Randy Jackson said, trying to defuse the tense situation that began when Cowell off-handedly addressed Seacrest as “sweetheart.”

“Don’t call me ‘sweetheart,’ ” Seacrest snarled. “I don’t want that kind of relationship.”

The pair’s efforts to provoke one another has always been part of the chemistry of the hit Fox show. But last night’s exchange seemed unusually nasty – and Cowell looked genuinely angry afterward.

“You’ve made this very uncomfortable, Ryan,” Cowell said.

“We’ll handle this another time,” Seacrest replied.