Brown released a two-minute video on his Web site on Monday apologizing to fans and saying he is sad and ashamed of his conduct.
He also says on the video that he has repeatedly apologized to Rihanna.
Brown was arrested Feb. 8 and later charged with assault likely to cause great bodily harm. He pleaded guilty to the assault charge last month and faces sentencing on Aug. 5.
He is slated to serve five years of probation and perform six months of community labor.
Brown says on the video he wanted to speak out earlier, but was advised not to by his lawyer.
The 20-year-old calls his actions "unacceptable."
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