Budweiser cans run through a filling machine at an Anheuser-Busch InBev brewery in Los Angeles. Associated Press

LONDON—Anheuser-Busch InBev NV is talking to banks about financing what could be a roughly £75 billion ($122 billion) deal to buy global beer rival  according to a person familiar with the matter.

A tie-up between the world's two largest brewing companies has been rumored for years, but a revival in global merger activity this year has sparked renewed speculation about a deal. AB InBev isn't in active discussions with SABMiller, said the person, explaining the company is waiting to line up its financing before making a formal approach.

Any deal would have to far surpass InBev's $52 billion acquisition of Anheuser-Busch in 2008, the largest deal in the sector.

The talks about financing come on the heels of an approach by SABMiller to buy Dutch brewer Heineken Markets Gu... More quote details and news » HEIA.AE in Your Value Your Change Short position NV, which Heineken said Sunday it had rejected. The U.K. brewer hasn't been discouraged by Heineken's initial rejection and would consider another bid, according to another person familiar with the discussions.

AB InBev had a nearly 20% share of the global beer market in 2013, according to data service Euromonitor. It is trailed by SABMiller, with a 9.6% share, and Heineken, with a 9.3% share.

Although a tie-up between the world's two biggest brewers would put control of nearly a third of global beer supply with one company, analysts say antitrust issues aren't insurmountable. AB InBev would likely have to sell SABMiller's stakes in two joint ventures, MillerCoors in the U.S. and CR Snow in China.

Buying SABMiller would catapult AB InBev into market-leading positions in Colombia and Peru, as well as many countries in Africa where the Budweiser maker has little presence.

AB InBev has a history of reshaping the beer industry with large-scale acquisitions. In 2004, Brazil's AmBev and Belgium's Interbrew merged to create the global No. 1 brewer by volume. Four years later, the new company bought Anheuser-Busch and became AB InBev.

The company has been steadily paying down debt it took on for its last big acquisition—when it bought the half of the Mexican brewer Grupo Modelo  completed in 2013.

With its free cash flow now increasing, industry watchers now say AB InBev is primed for its next big deal. "It's the first time in quite a few years that their balance sheet is sorted out," said Kris Kippers, an analysts at KBC in Brussels.

AB InBev has recently focused on boosting revenue through investments in sales and marketing, such as its sponsorship of the World Cup in Brazil. But the company's strength lies in cost-cutting, which provided the logic behind the Grupo Modelo deal and its purchase of Anheuser-Busch.

AB InBev's management team trimmed billions of dollars off those brewers' annual operating costs, helping to pay off the large debt that AB InBev took on to finance the deals.

But AB InBev may have to move quickly to buy SABMiller, maker of Foster's, Peroni and Miller.

The U.K.-listed brewer is interested in Heineken's eponymous beer brand, which it would distribute through its channels in Africa, according to the person familiar with SABMiller's discussions. The person added that pursuit of a deal with Heineken wasn't motivated by a desire to stave off a bid from AB InBev.

SAB's shares are up more than 40% since February, in part because of deal speculation.