Billionaire investor Carl Icahn said Thursday that he has spoken to Tim Cook and will be having dinner with the Apple CEO to discuss the "magnitude" of a stock buyback.
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"Spoke to Tim. Planning dinner in September. Tim believes in buyback and is doing one. What will be discussed is magnitude," Icahn tweeted @Carl_C_Icahn.
The activist investor revealed last week via Twitter that he had taken a large position in Apple, which is estimated to be worth more than $1 billion. Icahn told CNBC last Tuesday that a bigger buyback was a "no brainer" for Apple and that it would enhance the stock value tremendously, which he said was largely undervalued.
The stock jumped more than five percent on Icahn's news last week.
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Icahn's bet that the stock only has room to grow comes at a time when the company is bracing to make significant product launches, which would likely push the stock higher regardless, said Gene Munster, an analyst for Piper Jaffray.
"The next year is going to be a big year for Apple and he probably thought he might as well hold this meeting before that," Munster told CNBC last week after the announcement. "There's the investor side of it, which is to own the stock before the product cycle, and there's the activist investor side, which is probably to increase pressure to do a buyback."
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—By CNBC's Cadie Thompson. Follow her on Twitter @CadieThompson