LOS ANGELES, CA  [Thursday Aug.16.2007]  /Mix103FM.com/ -- Teenmusic.com reports that Madonna has issued a warning to "Summer Love" star Justin Timberlake: not to breathe a word about their super-secret duet.

Madonna and Timberlake collaborated on a new track in London earlier this year, but that's about all he can say about it.

JT says, "I don't want to tell you the name of the song because she'll either kill me or have me kill you."

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