UPDATE 1-Anheuser-Busch will not comment on Modelo reports

(Adds quotes from letters)

NEW YORK, June 16 (Reuters) - Anheuser-Busch Cos Inc (BUD.N: Quote, Profile, Research), the subject of a $46.3 billion bid by Belgian brewer InBev NV (INTB.BR: Quote, Profile, Research), refused to comment Monday on reports that it was pursuing a side deal with Mexico's Grupo Modelo. (GMODELOC.MX: Quote, Profile, Research).

"It is Anheuser-Busch's policy not to confirm, deny, comment on or speculate on rumors," Anheuser-Busch Chief Executive August Busch IV wrote in a letter to InBev Chief Executive Carlos Brito.

Busch's letter refers to an earlier letter Brito wrote that warned Anheuser-Busch, brewer of the popular Budweiser beer -- against pursuing deals with other companies while considering the $65 per share offer by InBev, which makes well known European beers Stella Artois and Beck's.

"As we have previously indicated, our board of directors is evaluating your proposal carefully and in the context of all relevant factors, including Anheuser-Busch's long-term strategic plan," Busch wrote in his letter.

"Our board will pursue the course of action that is in the best interests of Anheuser-Busch's stockholders and expects to make its determination in due course," he wrote.

Brito's letter, dated Sunday, cited press reports saying that Busch might have approached Grupo Modelo. Anheuser-Busch owns a 50 percent stake in Modelo, which makes Corona beer.

"We believe it is important for you and your board to understand that our proposal to combine with Anheuser-Busch... for $65 per share in cash is made on the basis of Anheuser-Busch's current assets, business and capital structure," Brito wrote.

Brito also urged Anheuser-Busch to explore InBev's offer before proceeding with alternative transactions, "especially if your shareholders will not be given the opportunity to vote on it."

InBev made an unsolicited offer for Anheuser-Bush on Wednesday. Such a deal would create the world's largest brewer. (Reporting by Robert MacMillan; Editing by Andre Grenon, Leslie Gevirtz)