The South African, 31, still has two years to run on his contract but with 31 goals from 79 games for the club, manager Mark Hughes wants to keep him for as long as possible.
"Discussions have been on-going for quite a while and we will continue to talk," chairman John Williams told the Lancashire Telegraph.
It is also believed that taks are still on going between Rovers and David Bentley and Stephen Warnock.