(Corrects to say Rial will advise 3G Capital founders as individual shareholders, not the firm 3G Capital, in 12th paragraph)

SAO PAULO/MEXICO CITY, Jan 11 (Reuters) - Brazilian retailer Americanas SA said on Wednesday its chief executive and chief financial officer resigned after the discovery of around 20 billion reais ($3.88 billion) in accounting "inconsistencies."

Lojas Americanas CEO Sergio Rial departed less than two weeks after taking the job, when he replaced Miguel Gutierrez.

Joao Guerra, a long-time Americanas executive not involved with accounting or financial management, will take over as CEO on an interim basis.

CFO Andre Covre also had just joined Lojas Americanas, long controlled by three Brazilian billionaires who founded 3G Capital.

In a statement, Americanas said the inconsistencies related to supplier financing operations in previous years including 2022. "The company estimates that the cash impact of the inconsistencies is not material," it said.

Internal inquiries and work by independent auditors will be needed to determine the impact of the inconsistencies on the company's financial statements, Americanas said.

Given this and "a change in the administration’s priorities," the two executives "communicated their decision not to remain in the company with immediate effect," the retailer said.

In a letter to employees seen by Reuters, Rial said Americanas has 8 billion reais in cash and will "keep paying suppliers and other liabilities on time". Rial also said the company will need to address its net equity position, which may require a capital raise, but that would not be the only option.

Rial will discuss the findings in a conference call with investors hosted by Banco BTG Pactual on Thursday morning, the bank confirmed.

The amount of accounting inconsistencies is larger than the company's net equity, 15 billion reais, said Fabrício Gonçalvez, CEO at Box Asset Management. "This is awful news for the retail sector, especially considering it happened with a large company such as Americanas", said Gonçalvez. "How can $3.9 billion escape from auditors?"

The amount is also almost twice Americanas' 10.7 billion reais market capitalization, according to Refinitiv data.

Despite his resignation, Rial will continue to advise the 3G Capital founders, the firm said.

In late 2021, founders of 3G Capital, which controls beverages maker Anheuser Busch Inbev and Kraft Heinz Co , reduced their stake in the retailer as part of a restructuring but continue to be "reference shareholders."

Brazilian retailers are under pressure from high borrowing costs. Americanas shares ended 2022 with a 68.7% slump, but since then have climbed about 24%.

The accounting problems will make the recently announced plan to migrate the company to U.S. markets unfeasible. It was delayed late last year. ($1 = 5.1600 reais) (Reporting by Peter Frontini in Sao Paulo and Carolina Pulice in Mexico City; Additional reporting by Tatiana Bautzer and Paula Laier in Sao Paulo; Editing by Christian Plumb)