Talk about Big Beer: If the rumors are true, most of the world’s suds -- delicious, adequate or downright atrocious -- soon will be made by one company.

Shares in SABMiller PLC, the world’s second-largest beer company, went through the roof Wednesday after its larger competitor firmed up plans to make an offer to combine the two brewers into one of the world’s largest companies. Louvain, Belgium-based Anheuser Busch Inbev SA said it could announce “a firm intention to make an offer” for London-based SABMiller or back off by Oct. 14.

“The board of SABMiller will review and respond as appropriate to any proposal which might be made,” the company said in a statement Wednesday responding to “press speculation” about a possible deal.

The combination of the world’s two largest brewers would be the biggest mergers-and-acquisition deal of the year, creating one of the largest companies in the world as measured by market capitalization. At $276 billion, the combined company’s valuation would be bigger than that of either General Electric Co. or JPMorgan Chase & Co. and more than one-half the size of Apple Inc.

The statements by the two companies came in the wake of recent events indicating that a deal is in the works, sending investors flocking to snatch up stock. Wednesday, SABMiller (LON:SAB) shares jumped more than 23 percent, to 3,718.18 British pence ($57.37), in London, while Anheuser Busch Inbev (EBR:ABI) shares rose more than 6 percent, to 113.60 euros ($115.41), in Brussels.

Rumors about a combination of the top beer makers have been circulating for months, but speculation heated up after SABMiller’s top shareholder Altria Group pulled out of two conferences this week and Felipe Dutra, Anheuser Busch Inbev’s chief financial officer, pulled out of an event last week, according to the Telegraph newspaper. These kind of moves suggest executives at both companies may be engaging in negotiations.

Global brewers have been consolidating for years amid rising costs as they seek to achieve economies of scale. In 2013, Anheuser Busch InBev bought Mexican beer giant Grupo Modelo SAB, maker of Corona and Victoria, for $20.1 billion.

The combination that could be in the final stages of talks now would bring together the historical American rivals Budweiser and Coors, unless U.S. anti-trust action were taken. 

Anheuser Busch InBev owns Budweiser, Beck’s and Stella Artois, as well as the Modelo brands, while SABMiller owns more than 200 beer brands, including Foster’s in Australia, Peroni in Italy and Olde English 800 malt liquor in the U.S.

The combination would likely face antitrust scrutiny that could require it to shed some of its assets. “The U.S. Department of Justice would almost certainly insist on the disposal of SAB’s stake in MillerCoors in the USA,” Trevor Stirling, a beverages analyst at Bernstein, told the Financial Times.