The "SexyBack" singer helped kick off the fourth season of The Ellen DeGeneres Show by performing his hit single in New York City's Central Park.

After the performance, DeGeneres brought up "the rumor that you and Cameron are engaged."

Sinking into his chair, Timberlake asked how she could put him on the spot in front of the 10,000 people in the crowd. "The only reason I need to know," DeGeneres said, "(is) I need to know, should I get a bridesmaid dress now or not?"

"Know what?" Timberlake said. "Go ahead and reserve one."

As the crowd burst into cheers, DeGeneres asked when she'd get to wear it. "I've got a busy schedule," she said.

"The only thing is," Timberlake said, "you'll have to stay the same size for the next 15 years."

The crowd could not mask its disappointment. Pressed as to where things stand between him and Diaz, Timberlake said of recent press reports, "Funny thing, one week we're getting married, one week we've broken up. I can't keep up with it."

Assuring him he could keep up with it, DeGeneres asked whether, in fact, he and Diaz are engaged. "We're not engaged," he replied, before joking, "She hasn't given me a ring. I've waited for her to get down on one knee and ask."

Timberlake also spoke about his 'N Sync bandmate Lance Bass, who recently came out. "That must've been a huge thing for him," said DeGeneres, noting that Bass kept his being gay a secret for fear of jeopardizing the group's success.

Said Timberlake, "Let's all be honest. I don't think we didn't know. Lance is one of my greatest friends. I'm more happy for him than I've ever been. … He gets to live his life the way he wants to live his life."