Investor Carl Icahn tweeted that he and Apple Chief Executive Tim Cook would talk over dinner about the size of the company's stock buyback.

"Spoke to Tim," Icahn tweeted. "Planning dinner in September. Tim believes in buyback and is doing one. What will be discussed is magnitude."

A few days ago, Icahn revealed he had bought about $1 billion in Apple stock.

Though the buyback, Icahn wants to see it go as high as $150 billion, according to some reports.

Icahn's tweet came during yesterday's three-hour shutdown of stock trading on Nasdaq.