Anheuser already owns a roughly 50% non-controlling stake in Modelo and a combination of the two could make the company too big to be absorbed by InBev.
This comes a day after Belgium's InBev, which makes Stella Artois and Beck's beers, announced a $46.3 billion bid for top U.S. brewer Anheuser-Busch, which makes Budweiser.
Meanwhile, all three major rating agencies on Thursday said they may cut their ratings on Anheuser-Busch after InBev's Wednesday offer.
"We believe that if the transaction proceeds, and includes a significant amount of debt financing as indicated by InBev, credit measures will weaken well below Anheuser-Busch's current levels," Standard & Poor's said in a statement.
S&P and Fitch Ratings both rate Anheuser "A," and Moody's Investors Service rates the company "A2," all the sixth-highest investment grade.
"While it is unclear if the bid will go through and it could take some time for more certainty to develop, there are several ways in which the bid could pressure ratings," Moody's said in a statement.
It would be negative for Anheuser's ratings if InBev incurs substantial leverage to make the deal happen and is itself less creditworthy than Anheuser, or if it levers up the U.S. company to use the U.S. cash flows to repay the debt, Moody's said.
InBev Would Have to Raise: Analysts
The InBev offer amounts to $65 a share, a more than 11 percent premium of Anheuser's closing price on Tuesday and 24 percent above the price before reports of a possible bid emerged last month.
Analysts told CNBC earlier that InBev would probably need to ratchet up that bid.
"We respect the Anheuser-Busch board a lot ... we admire them a lot and we think that the business rationale is very strong," InBev Chief Executive Carlos Brito said in a video statement on InBev's website.
Brito said a combined Anheuser-InBev would retain top managers and board members from both sides, suggesting InBev was looking for a friendly merger of equals rather than a hostile takeover. "The combined company would be run by the combined entities," he said, without divulging whether he would seek to head the new beer behemoth himself.
Despite the fact that the deal would be the biggest ever alcoholic drinks takeover, InBev should have no problem raising the money, Trevor Stirling, senior research analyst for European beverages at Sanford Bernstein told "Squawk Box Europe." It's also unlikely another brewer or beverage company would come in and try and hijack the deal, he added.
"I don't think they would have gone public with this if they didn't have reasonable comfort from the banks," Stirling said.