The world’s two biggest beer behemoths are considering the largest megamerger in brewing history, after Budweiser giant Anheuser-Busch InBev said Wednesday it had pitched a takeover of SABMiller, its chief rival.

The deal would fold in some of the world’s best-selling beers beneath a $245 billion hyper-profitable brewing empire. But it would also likely put antitrust authorities on high alert, over fears that the the loss of competition could drive up prices.

“What a terrible, terrible idea. This should be dead on arrival at the DOJ,” or Department of Justice, said Diana Moss, president of the American Antitrust Institute. “There would be grave concerns over their power to control price … and the effects on the craft-brewing industry would be devastating.”

The long-speculated merger would combine Budweiser, Coors, Miller, Peroni and other brands under one roof, controlling roughly a third of the world’s beer supply and about half of the industry’s profits.

It could also give the companies huge cost savings on ingredients, packaging, distribution and the many other expenses that come with running a worldwide enterprise.

But the offer could also be rejected. In a statement, the U.K.-based SABMiller said the firm had yet to receive the formal proposal. Investors were nevertheless excited: Shares in London for SAB boomed more than 20 percent, while the Belgium-based A-B InBev’s stock jumped more than 7 percent.

A-B InBev and MillerCoors, SABMiller’s partnership with Molson Coors, already control about 70 percent of the American beer market. But a takeover would give them added energy in their campaign to boost slumping beer sales and combat the rise of smaller craft brewers.

The merger would also give both giants more resources in tackling the growing beer markets outside the U.S., including A-B InBev’s push in Latin America and SABMiller’s hold on Africa.

The beer industry has, as with airlines and food conglomerates, embarked on years of big, incestuous industry pairings. Anheuser-Busch InBev was born of the world’s biggest beer merger, in 2008, after the stalwart American brewer was taken over by InBev — itself a product of the 2004 merger of Belgium’s Interbrew and Brazil’s AmBev.

A-B InBev has pushed hard to scoop up new business lines, too, in a fast-and-furious takeover style that has alerted antitrust authorities in the past.

When A-B InBev in 2012 pushed to buy the entirety of Grupo Modelo, the Mexican brewer of Corona, the DOJ fought back, saying the $20 billion deal would hurt American drinkers by removing a big competitive influence.

After months of negotiations, the brewer modified terms of the deal and the merger continued. Among the new terms: Constellation Brands, a New York-based wine and spirits conglomerate, would get Corona’s license to sell in the U.S., in hopes that competitor could help set prices outside of A-B InBev’s control.

An antitrust crackdown on the latest A-B InBev deal could force the companies to give up territory or sell off current holdings. Analysts at investment researcher Bernstein, for instance, suggested SAB may have to relinquish its claim to the MillerCoors business in the U.S.

But Moss, of the American Antitrust Institute, said there’s one big problem to permitting that kind of arrangement. Because both brewers are so big, and the industry is already so consolidated, it could be hard to find another firm powerful enough to compete on production, distribution, marketing and everything else.

“Who would be able to even buy any of those assets, and have an actual competitive presence in the market?” Moss said. “In the U.S. market, there would hardly be anyone left.”