Icahn seeks $50 billion Apple buyback: Source

Billionaire investor Carl Icahn will submit a proposal to Apple's shareholders at the company's annual meeting, a source told CNBC. The proposal calls for Apple to buy back $50 billion in stock.

Earlier Wednesday, Icahn announced in a tweet he has notified Apple that he intends to make a push for a vote on a buyback increase.

"Gave $AAPL notice we'll be making a precatory proposal to call for vote to increase buyback program, although not at $150 billion level," Icahn wrote in a tweet. A precatory proposal would not be legally binding.

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Carl Icahn

Icahn had been pushing for Apple to institute a $150 billion buyback. Icahn owns approximately 0.5 percent of Apple's outstanding shares, according to Thomson Reuters data.

Apple shares, which had been trading slightly in the red for most of the session, remained lower following the news.

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"Earlier this year we more than doubled our capital return program to $100 billion, including the largest share repurchase authorization in history," according to a statement from Apple. "As part of our regular review process, we are once again actively seeking our shareholders' input on our program, and as we said in October, the management team and our board are engaged in an ongoing discussion about it which is thoughtful and deliberate. We will announce any changes to our current program in the first part of calendar 2014."

Icahn also revealed in an interview with Time magazine that he filed a shareholder proposal with the iPhone maker on Nov. 26 to persuade the company to share some of its $147 billion cash hold with stockholders.

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—Written by CNBC's JeeYeon Park (Follow JeeYeon on Twitter: @JeeYeonParkCNBC). CNBC's David Faber contributed to this report.