Cesar was named in the Brazil squad on Tuesday for a friendly against South Africa in March, with national team coach Luiz Felipe Scolari appearing to suggest that his move to Canada was all but complete.
But Nelsen insisted there was nothing to announce just yet.
"At the moment, I can't really comment because nothing has been finalised," he told O Globo.
"I haven't spoken to Julio Cesar for a couple of days, so I don't know about what Scolari said.
"It is something that would be really nice for the Toronto fans and the community to have a player of his skill, expertise and experience.
"I might have to give Scolari a call to see if it has happened."
Cesar has made just one FA Cup appearance for QPR this season.
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