Warren Buffett has sold IBM shares, and 'revalued' tech icon downward, cites 'big strong competitors'

Warren Buffett sells off a third of his stake in IBM

IBM has lost the confidence of one of its biggest investors, Berkshire Hathaway Chairman and CEO Warren Buffett.

Buffett, who owned about 81 million shares of IBM at the end of 2016, sold off about a third of that stake in the first and second quarters of 2017, he told CNBC.

"I don't value IBM the same way that I did 6 years ago when I started buying... I've revalued it somewhat downward," Buffett told CNBC. "When it got above $180 we actually sold a reasonable amount of stock."

Buffett said IBM hadn't performed the way he had expected -- or the way IBM's management had expected -- when he first started buying the shares six years ago.

"I think if you look back at what they were projecting and how they thought the business would develop I would say what they've run into is some pretty tough competitors," Buffett said. "IBM is a big strong company, but they've got big strong competitors too."

Berkshire Hathaway still owns more than 50 million shares of IBM and with shares now trading below $160, Buffett says he has stopped selling.

For more on Buffett's moves and his reasoning behind the sale of IBM, tune into Squawk Box on CNBC at 6 am Eastern time Friday.