"I know where I will be playing next season and I will announce it in the coming days," he told reporters at Belgium's World Cup camp near Moscow on Tuesday.
He dismissed the idea that uncertainty over his future after his contract runs out might have affected his performance ahead of a possible selection for Belgium against England on Thursday.
"I'm at the end of my contract and I want to be free in my mind. That's why I'll be announcing it next week," added the 30-year-old, whose name has also been linked with Arsenal and whose Manchester United contract runs out at the end of this month.
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Asked if he would reveal his plans on Sunday, July 1, he replied: "Yes."
Belgium coach Roberto Martinez has said he will rotate his line-up for the Group G decider against England in Kaliningrad, which could mean Fellaini starts for the first time in this World Cup.
With both teams through to the next round, Belgium will play either Colombia, Senegal or Japan on Monday or Tuesday.
(Reporting by Alastair Macdonald; @macdonaldrtr, editing by Pritha Sarkar)
