"Whitney has admitted that she had to conquer a drug addiction and that takes all of her energy, but she also has had a very difficult time giving up cigarettes," he told Los Angeles radio station KOST 103.5 FM. "I know that she's committed to do it. I know that she loves music and that, you know, right now she's dealing with that situation. And we're not going to make a record or an album until that golden voice, you know, is there and is fully capable of just knocking everybody out."
Despite her late-career struggles, peers said Houston will always be remembered as "the voice."
"She could sing a song like nobody ever could and nobody ever will," said veteran songwriter Diane Warren. "She's the best -- the best singer we've had in the last 40 years, unarguably.
"She didn't have to stand with things blowing up and special effects," Warren added. "She just sang."
See the full story on "One Moment in Time: The Life of Whitney Houston," a two-hour "20/20" special, TONIGHT at 9 p.m. ET.