The 25-year-old, who is currently on loan at the Brazilian side, has contributed three goals and an assist from nine league appearances so far this season.
Flamengo have already agreed an option with United where they can push through a £17m permanent transfer at the end of the campaign.
However, Globo Esporte claims that the Scarlet-Black want to negotiate a lower fee for Pereira over the coming months.
Flamengo officials allegedly feel that it would not be reasonable to pay such a fee in the current financial climate.
Pereira has a contract at Old Trafford until the end of the 2022-23 campaign.