According to reports in the French media, Nonu has agreed a new verbal deal in principle with the club, but is yet to sign on the dotted line.
He joined Toulon after the 2015 World Cup and his original deal is due to expire in June 2017.
“We agreed to the oral, we just have to write it. If everything goes well, we will announce it quickly,” Toulon owner Mourad Boudjellal was quoted as saying.
Nonu is reportedly on a current deal worth around $1 million per season.