Anheuser-Busch InBev's $11 billion asset sale to Japan's Asahi could hurt competition in Australia's cider sector and may also do the same for beer, the country's competition regulator warned on Thursday.

AB InBev's planned sale of Carlton & United Breweries (CUB) is part of the world's largest brewer's drive to lower debt after buying SABMiller in 2016. It has been busy selling assets and listed its Asian business in Hong Kong in September.

"The proposed acquisition would combine the two largest suppliers of cider in a highly concentrated market," the Australian Competition and Consumer Commission (ACCC) said in its preliminary view, adding the combined business would control about two thirds of cider sales in the country.

Asahi might also act as a competitive constraint on the two largest beer brewers in Australia - CUB and Lion - and has "the potential to be an even bigger threat in future," the ACCC said. Belgium-based AB InBev had aimed to close the sale in the first quarter of 2020. The ACCC said it would make a final decision on March 19.

Asahi would likely be required to dispose of a cider brand, but the impact was manageable, Bernstein analysts said. In the worst case scenario, Asahi might offer to shed AB InBev beer brands Beck's, Stella Artois and Budweiser locally. Losing Corona would likely be a deal breaker, they said.

Jefferies analyst Edward Mundy, said he expected brand disposals, and a possible delay to the deal closure. "We do not believe that this preliminary ruling would be insurmountable to the deal taking place," he said.

Asahi said it was not planning any changes for now, and would continue providing the ACCC with information. AB InBev said it would be working with Asahi and the regulator to secure approval of the deal.

Asahi shares fell to a three-month low and closed down 1.1 percent on Thursday. AB InBev shares sunk to a nine-month low and were down 1.9 percent at 1320 GMT, making them one of the weakest performers in the FTSEurofirst 300 index of leading European stocks. The deal would propel Asahi into the major league of brewers, although still place it well behind leaders AB InBev and Heineken.