Buffett is a co-investor in Kraft with its owner Brazilian private equity firm 3G Capital. 3G has made a name for itself acquiring well-known consumer companies and squeezing out costs. The food industry's favorite parlor game over the past year has been guessing what Kraft's next acquisition will be, and many had placed their bets on Mondelez, which owns such brands as Oreo cookies. Mondelez was part of Kraft until it was spun off into a separate company in 2012.
Buffett was asked in an interview with CNBC's "Squawk Alley" whether Kraft would be interested in buying Mondelez.
"I think the answer is no on that," he said.
Buffett's answer left analysts at RBC Capital Markets "pretty confused," the firm's David Palmer wrote in a research note. However, Palmer identified five reasons that could be influencing Buffett.
3G's cost-cutting prowess would have limited impact on some of Mondelez's biggest challenges: powerful retailers that can squeeze brands on price and slowing sales that require investment in sales and marketing.
Kraft's failed bid for dial soap owner Unilever meanwhile, shows the company is interested in the home and personal care sector, which could offer Kraft more room to grow.
Plus, activist investors own significant shares of Mondelez, and the company has minority stakes in Keurig Green Mountain and Jacobs Douwe Egberts. Both present unknown issues for 3G Capital and Buffett, Palmer wrote.
Buffett said "the answer is no," but he really means "not now" because food companies are getting cheaper thanks to Amazon, Palmer wrote.
"In other words, Mr. Buffett and 3G are not going to get in the way of a good discount that will impact Mondelez's stock more than the direct Amazon effect is impacting Mondelez's business," Palmer wrote.
Berkshire Hathaway did not immediately respond to CNBC's request for comment.