Former Microsoft CEO Bill Gates doesn't agree with Bono's prediction of an AIDS-free generation by 2015.

Bono, the frontman for U2, said in a This Week interview that an AIDS-free generation was within sight.

“There's a chance of having the first AIDS-free generation by 2015, 2016. We can see it. We could lose that, if we lose the political will,” Bono told George Stephanopoulos on Sunday, World AIDS Day.

(Related: U2's Bono on World AIDS Day: The end is near.)

Appearing on CNN, Gates appeared to disagree.

“We're making great progress on AIDS,” Gates said. “But we have over 30 million people who are living with the disease. We don't have a cure. And so we have to keep them on drugs to keep them alive and that requires not only generosity but getting very innovative about how we reach that kind of a number. We need a vaccine, or a tool to prevent people from getting infected. So there is still a lot to be done, even though we have made progress. We're going to be living with some level of AIDS for decades to come.”

(Related: Obama pledges $100 million to cure HIV/AIDS.)