"There's a strong possibility (of a move to Fluminense) but at the moment I can't confirm anything because I have a contract with Chelsea," Deco, who obtained Portuguese citizenship in 2002, told a news conference on Tuesday.
"I'm only going to decide after the World Cup," Deco, keen to return after leaving Brazil for Europe 13 years ago, said in Indaiatuba, where he grew up in the interior of Sao Paulo state, on the second anniversary of his Deco20 Institute for children.
The 32-year-old Deco, who will join up with the Portugal squad on Wednesday for their World Cup preparations, said he would choose the best club project available.
"I'm not coming (to Brazil) to end my career. I'm coming to play. I believe I have a few more good years to play at a high level," he said.
Deco, who has a year left on his contract with Chelsea, won the European Champions League with Porto in 2004 and Barcelona in 2006.
He joined Chelsea in June 2008 when Luiz Felipe Scolari, his former coach with the Portugal team, was in charge.
However, he has struggled for first team chances due to injuries and low form and missed their recent Premier League and FA Cup double celebrations in London.
Deco helped Portugal reach the Euro 2004 final and the 2006 World Cup semi-finals.
Portugal face Brazil, Ivory Coast and North Korea at the 2010 finals in South Africa starting on June 11.
