Kraft Heinz, the maker of Velveeta, Kool-Aid, and Grey Poupon, on Friday said it had made an offer to buy Unilever for $143 billion in what could be the largest food and beverage deal of all time.

Unilever, however, said it isn’t interested in the $50-per-share deal, which represented an 18 percent premium on Thursday’s share price. The British-Dutch company, which has 400 brands including Hellman’s, Ben & Jerry’s, and Vaseline, said it ‘‘rejected the proposal as it sees no merit, either financial or strategic, for Unilever’s shareholders.’’

‘‘Unilever,’’ the company added, ‘‘does not see the basis for any further discussions.’’

But Kraft says it isn’t taking ‘‘no’’ for an answer, and analysts say the company will probably sweeten its cash-and-stock offer as it looks to Unilever to help expand its international reach.

Kraft said in a statement that it is ‘‘working to reach agreement on the terms of a transaction.’’

If the two packaged-food giants were to reach a deal, it would bring together hundreds of iconic brands, including Lunchables and Lipton, and Maxwell House and Marmite. The combined company would have annual sales of nearly $85 billion a year, just behind Nestle’s 2016 revenue of roughly $89 billion.

The purchase would also help US-centric Kraft Heinz tap into European and Asian markets, which make up about 70 percent of Unilever’s annual revenue, and would help it expand beyond food and drink products.

‘‘Geographically speaking, these two companies are very complementary,’’ said Paul Hickman, an analyst at Edison Investment Research in London. ‘‘You can see how putting them together would make sense.’’

Packaged-food companies have been under pressure to consolidate in recent years amid slowing growth, increased competition, and heightened demand for more healthful foods. Still, analysts said they were surprised by the offer. Kraft Heinz is in the midst of cutting costs following the multibillion-dollar deal that brought together the J. Heinz Co. with Kraft Foods in 2015. Today, Warren Buffett’s Berkshire Hathaway and Brazilian investment firm 3G Capital own about 51 percent of Kraft Heinz. Buffett sits on the company’s board.

‘‘For me, the deal makes no sense,’’ said Michael Hewson, chief analyst for CMC Markets in London. ‘‘Kraft could get a very big dose of indigestion if they decided to pony up for this one.’’

For one, he said, Unilever — with roughly $58.7 billion in annual revenue and 168,000 employees — is larger than Kraft Heinz, which has $26.49 billion in annual revenue and 42,000 employees.

And, he said, the merger of two of the world’s largest packaged-food companies could also raise concerns among antitrust regulators in the United States and Europe, Hewson said.

And, he added, Unilever shareholders could be wary of the deal.

‘‘Look at the way Unilever has performed over the last 20 years: Steady income growth — through recessions, through booms,’’ he said. ‘‘I’m not convinced long-term Unilever investors would want to pass that up.’’