The battle of the billionaires took another twist on Friday.
In his first public comments following the disclosure of activist investor Carl Icahn's stake in Herbalife, hedge fund manager Bill Ackman, who made $1 billion short bet against the stock, told CNBC he remains convinced that "Herbalife is a pyramid scheme."
Ackman's statement read, "We invest based on a careful analysis of the facts. After 18 months of due diligence, we have concluded that it is a certainty that Herbalife is a pyramid scheme. Our conclusions are unaffected by who is on the other side of the investment. Our goal was to shine a spotlight on Herbalife. To the extent Mr. Icahn is helping achieve this objective, we welcome his involvement."
Last month, Icahn and Ackman captivated CNBC viewers with their now famous heated call-in interview on "Fast Money Halftime Report," which featured allegations, insults, and counter-allegations.
(Read More: Ackman, Icahn Hurl Accusations, Insults)
At the core of the dispute was at decade old dispute and Icahn's outrage with Ackman over the latter's short position on Herbalife.
Now according to a 13D filing on Thursday, it was disclosed that Icahn bought 14 million shares of Herbalife, giving him a 12.98 percent stake in the nutritional supplement marketer.
(Programming note: Carl Icahn is scheduled to appear on "Fast Money Halftime Report" Friday at noon eastern time)
Icahn told CNBC's "Fast Money" on Thursday that he's done a great deal of research on Herbalife and that he doesn't make investments like this lightly.
(Read More: Icahn Takes a 12.9% Stake in Herbalife)
Icahn has now replaced Third Point's Dan Loeb — who told investors in January that he had bought an 8 percent stake in Herbalife — as the most prominent rival to the short position that Ackman's Pershing Square has taken.
—Reuters also contributed to this report.