Citing a need for more rest after a physical and emotional breakdown that occurred in July, Mariah Carey has postponed an eagerly anticipated interview with ABC News's Barbara Walters, says her publicist, Cindi Berger. The face-to-face was set to air on "20/20" Sept. 12, the day after the soundtrack album to the pop diva's upcoming movie "Glitter" arrives in stores. ("Glitter" itself opens on Sept. 21, after it was pushed back from an original Aug. 31 release date. The film is Carey's first starring vehicle. But her hospitalization stymied plans for her to promote it, a situation which partly explained the delay of its release.) Since her two-week treatment, Carey, 31, has been with her mother, under a doctor's care. The music star recently posted a voice message on her official Web site for her fans. Its message: "Hey guys, I'm just checking in, letting you know that I love you. I'm reading the letters you wrote me, and you always make me smile, no matter what. I'll call you soon, bye." Carey's representatives had promised ABC that the singer would discuss the reasons behind her hospitalization, which began on July 26, when she was taken to a facility in suburban New York. She was later moved to a Connecticut hospital. According to ABCNEWS.com, upon learning about Carey's cancellation, Walters said: "We were concerned to hear that Ms. Carey would be unable to do the interview at this time, and wish her well."