Democratic candidates take the stage together for the first time as they jockey for position in the race to take on President Trump in 2020.2020 Electionsread more
The issue over health insurance marked the first stark divide among the candidates, and sparked a heated back-and-forth between many of the candidates on stage.Politicsread more
In a strategy to draw attention away from Wednesday's Democratic debate, President Donald Trump's reelection campaign bought out YouTube's "masthead," the leading...2020 Electionsread more
Virginia Sen. Mark Warner breaks down the idea behind a bipartisan bill he introduced to provide more transparency in Big Tech.Technologyread more
The Federal Aviation Administration said on Wednesday that is has found an issue with the Boeing 737 Max that the manufacturer must address before it lifts the grounding...Airlinesread more
Tesla is working on new battery cell designs, and a way to make their own cells, with R&D teams in a lab near its car plant in Fremont, California.Technologyread more
These attacks have given the public the opportunity to examine the problems associated with ransomware, where corporations -- not obligated to disclose these attacks -- have...Technologyread more
"As a private company we don't have the tools to make the Russian government stop," Facebook CEO Mark Zuckerberg said at the Aspen Ideas Conference on Wednesday. "We can...Technologyread more
Something unusual is happening in financial markets, and it could mean more gains lie ahead for stocks, if history is any indication.Marketsread more
Underneath the impressive market rally is a trend that doesn't seem quite right, according to J.P. Morgan.Marketsread more
Wi-Fi 6 will be the next-generation wireless standard. Along with 5G, it will represent the next big shift in connectivity and data, said Irving Tan, senior vice president and...Shaping the futureread more
The letter, issued in conjunction with Icahn's new website "Shareholders Square Table," comes after Icahn urged Cook to use Apple's $150 billion in surplus cash to buy back company shares.
Icahn is scheduled for a live interview on "Fast Money Halftime" with Scott Wapner at noon EDT Thursday.
(Read more: Apple now hordes 10% of US corporate cash)
In the letter, Icahn praises Cook's leadership, but says the discussed share buyback needs to be substantial.
(Read more: Text of Icahn's letter to Apple)
"We want to be very clear that we could not be more supportive of you, the existing management team, the culture at Apple and the innovative spirit it engenders. The criticism we have as shareholders has nothing to do with your management leadership or operational strategy," the letter says. "Our criticism relates to one thing only: the size and timeframe of Apple's buyback program. It is obvious to us that it should be much bigger and immediate."
Apple shares were up Thursday. (For the latest stock price, click here.)
Biggest announced share buybacks in history.
The letter says Icahn's stake in the technology giant is now 4.7 million shares, up from 4 million, making his total stake roughly $2.46 billion. He said he would withhold his shares from the tender offer.
The letter says his increased investment in Apple reflects "our belief the market continues to dramatically undervalue the company."
"From our perspective, Apple is the world's greatest consumer product innovator and has one of the strongest and most respected brand names in history," the letter says.
(Read more: Ex-Apple CEO Sculley: Cook should ignore Icahn)
In an earlier interview with CNBC, Icahn said he would not be dropping this issue.
"I feel very strongly about this," Icahn told CNBC after his meeting with Cook in September. "I can't promise you the stock will go up and I can't promise you they will do the buyback. But I can promise you that I'm not going away until they hear a lot more from me concerning this."
(Read more: Icahn's dinner with Cook)
The letter says Apple's board does not include someone "with a track record as an investment professional."
"In my opinion, any further delay in executing the buyback we hereby propose will reflect this lack of expertise on the board," it adds. "The timing for a larger buyback is still ripe, but the opportunity will not last forever."
Not everyone welcomed Icahn's statement, though. The legendary bond investor Bill Gross took to Icahn's new favorite medium, Twitter, to respond.