Fluminense are planning to unveil the signing of Deco later this month.
Deco has a year left on his current contract at Stamford Bridge, but the 32-year-old midfielder has made little secret of his desire to move back to his homeland.
The Brazilian-born Portuguese international has been waiting until the end of the World Cup before finalising the details.
Now with Portugal out, he is negotiating the final details of his release - but Fluminense are already planning to unveil his signing on July 15.
"If Chelsea let me go, I have given Fluminense my word - although I have not signed any pre-contract," Deco is quoted as saying by the Daily Star.
"If I finish my time in London, then I will go to play in Brazil."
It is understood Deco will sign an 18-month deal with Fluminense.