Anheuser-Busch called a review of the account in July, shortlisting Euro RSCG London and the fellow incumbent Rainey Kelly Campbell Roalfe/Y&R alongside the two finalists.
The account review was run by the Budweiser UK marketing manager, Vicki Kipling.
The process marked the first time the UK office of the US-based brewing giant was afforded the freedom to appoint its own agency.
Historically, DDB, Anheuser-Busch's global network agency, has handled most campaigns, although RKCR/Y&R had created work for Budweiser's sponsorship deals since joining the roster in 2004.
A spokeswoman for Budweiser denied a decision had been made, and said that a statement about the review would be released on Friday. Fallon and DDB London declined to comment.