According to La Gazzetta dello Sport, Ronaldo would leave Juventus for free next summer with no terms agreed for an extension.
Juventus are expected to push for a new deal over the next 12 months, but the Portugal captain is also keen to return to Sporting Lisbon, where he started his senior career.
Ronaldo has been heavily linked with returns to Real Madrid and Manchester United over the past 12 months.
The 36-year-old was the top scorer in Serie A last season with 29 goals in 33 games.
Meanwhile, Juventus Sporting director, Federico Cherubini, is adamant that Ronaldo will stay at the Allianz for some time.
“We haven’t had any indication on the part of Cristiano Ronaldo [that he wants to leave],” Cherubini said earlier this month.
“We don’t need to talk about a transfer and Juventus do not want to sell him. We are talking about a player who scored 36 goals in 44 games last season.
“We are very happy that Ronaldo will be with the squad after his holiday.”