The stake sale incorporates some 57.6 million common shares, representing 11.7% of Assaí's share capital.
The group issued a statement that said the sale will be implemented through an accelerated book building process, executed by the São Paulo stock exchange (B3), in accordance with the applicable rules and regulations.
Casino said it will inform the market of the result of such a process.
Earlier, Casino announced it had reached an agreement in principle with the French government to defer payment of the group's tax and social security liabilities due between May and September 2023.
The group has been beset with debt following a string of acquisitions and by declining revenues in a competitive domestic market.
In May, the company started court-backed negotiations with its creditors, while weighing two tie-up bids from wealthy investors.
The agreement with the government would help Casino to preserve its liquidity throughout the conciliation procedure with creditors opened on May 25.
The agreement represents an amount of around €300 million.
Casino said all the financial creditors would be asked to agree, for the duration of the proceedings, to a standstill on any interest payments and other fees and principal instalments owed over this period by the group companies benefiting from the negotiations.
French Markets Regulator
Furthermore, the French markets regulator AMF said in a filing that one of Casino's top investors, billionaire Marc Ladreit de Lacharriere, had become Casino's second-biggest shareholder.
Ladreit de Lacharriere, 82, now owns about 12% of the French retailer after the businessman agreed to convert bonds issued by Casino's controlling holding Rallye into shares, the filing said.