Icahn took to his official Twitter account on Tuesday to tell followers that he believes Apple is "extremely undervalued" at its current share price. He is the majority shareholder of diversified holding company Icahn Enterprises, which had $15.39 billion in revenue in fiscal 2012.
The billionaire also revealed he had a conversation with Apple's CEO on Tuesday, in which Icahn shared his belief that "a larger buyback should be done now." Apple announced plans to boost its quarterly dividend and buy back shares at a cost of $100 billion through 2015.
Icahn said Tuesday that he plans to speak with Cook "again shortly." After his tweets were published, shares of AAPL shot up by more than 4 percent.
Update: After Icahn's comments gained publicity, Apple offered comment to The Wall Street Journal: "We appreciate the interest and investment of all our shareholders. Tim had a very positive conversation with Mr. Icahn today."
Apple spent $16 billion last quarter alone on repurchasing 36 million in shares. The original schedule had called for the company to buy 10 million in shares in the third quarter, but Apple apparently decided to push harder and buy at an average share price of $444.44 ??more than $250 off from the company's high of $702.10 reached last September.
The investor has made headlines in recent weeks for his opposition to Dell's attempts to take the company private. Icahn opened his Twitter account in June with a joke about his ongoing spat with the PC maker: "Twitter is great. I like it almost as much as I like Dell."
While Icahn's feuds with Michael Dell and the Dell Board of Directors are well known, the billionaire's bullish take on Apple wasn't revealed until Tuesday.