Michael Jackson's still grieving mother Katherine tells Oprah next week that she warned him drug abuse could kill him.

Oprah asked, "Had you ever spoken to him about his addiction?"

"I spoke to him about them once. I was telling him I didn't want to hear one day he had overdosed because it would break my heart. It would kill me too. But he kept saying he wasn't on anything. He said, 'Mother you don't believe me! My own mother doesn't believe me!'"

The Katharine Jackson interview airs Monday on Oprah.