Caixa's investment bank will lead the sale with the investment banking units of Bank of America Corp, Morgan Stanley and UBS AG, the source added, asking for anonymity to discuss the private hiring.

XP Investimentos SA was hired to distribute the offering to retail investors. Caixa will define a target for the participation of individuals in the offering, the source added.

Reuters reported in February that Caixa sought to divest from Petrobras, as the oil company is known, as a way to raise cash to pay for bonds it sold to the Brazilian government between 2007 and 2013.

Brazilian newspaper Valor Economico published the banks' hiring earlier on Monday.