Warren Buffett said Monday that he has "absolutely no intention" of selling his stake in Kraft Heinz (KHC) - Get Report , even as he admitted he likely overpaid for his near 27% holding in the packaged food group and wasn't surprised by the $15 billion writedown on two of its key brand assets.

Speaking with CNBC's Beck Quick in Omaha, Buffett said he wasn't going to "pull the plug" on Berkshire Hathaway's holding in the group, who's shares fell to a record low Friday after it posted much weaker-than-expected fourth quarter earnings and warned of a "step backwards" for the business in 2019.

"That's not our style, we're partners in this with 3G," Buffett said, referring the Brazil-based private equity group with which it has a combined 50% stake in Kraft Heinz. "I have no intention of selling and no intention of buying."

Kraft Heinz shares were marked 0.6% higher in the opening minutes of trading Monday and changing hands at $35.16 each. The stock plunged more than 27.4% during Friday trading, lopping more than $17 billion from its market value, after a dismal fourth quarter, coupled with an SEC notice and a grim 2019 outlook.

Kraft Heinz said Thursday that it expects to "take a step backwards" this year after writing down the value of some of its key brands, including Kraft and Oscar Mayer, by as much as $15.4 billion. The group, which is one of Buffett's key investments, sees 2019 earnings in the region of $6.3 billion to $6.5 billion, down 8.24% from last year at the higher end and well shy of the Street consensus forecast of $7.5 billion.

The company also slashed its dividend to 40 cents per share after adjusted fourth quarter earnings came in 10 cents shy of the consensus forecast at 84 cents per share.

Kraft Heinz has seen a steady decline in market share for its key brands, thanks in part to shifting consumer habits towards healthier options and competition from private label alternatives. It brought forward two years of investment plans into 2018, spending around $300 million in order to drive growth and develop its product pipeline, but fourth quarter net sales still fell shy of analysts forecasts and rose only 0.7% from last year to $6.9 billion.

"Where we fell short in 2018 was operations. Specifically, our entire EBITDA miss was driven by net savings versus expectations within our United States supply chain," said CEO Bernardo Hees. "There is no question we are disappointed that profitability did not ramp up with consumption gains as anticipated. We are overly optimistic on delivering savings that did not materialize by year-end."

"For that, we take full responsibility. And we have taken steps to ensure this does not happen again by touching planning process, procedures and organization structure," Hees added.

Kraft also said it had received a subpoena in October "associated with an investigation into" its accounting policies, procedures and internal controls related to its "procurement function."

This includes "agreements, side agreements, and changes or modifications to its agreements with its vendors," the company said. "Following this initial SEC document request, the Company together with external counsel launched an investigation into the procurement area."

"We continue to cooperate fully with the SEC and at this time the Company does not expect matters subject to the investigation to be material. For context, this $25 million increase to costs of products sold compares an annual procurement spend of over $11 billion annually for the total company," Kraft Heinz spokesman Michael Mullen told TheStreet in an email.

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