Black Sabbath star Geezer Butler has sparked rumours the rock veterans will be hanging up their instruments after completing their current world tour, by insisting the trek will "probably be the last".

The Paranoid hitmakers kicked off a mammoth series of dates in Australia earlier this year (13), taking in cities in North America, Britain, New Zealand, Germany, France, Chile and Brazil.

However, Butler, 64, insists touring is "getting tough" and he fears they may never hit the road again after the shows conclude in their hometown of Birmingham, England in December (13).

He tells the Chicago Sun-Times, "It probably will be the last time, will probably be the last tour... I just got a feeling. It's getting tough, it really is. I can't lie about that. I'm old now. It really is tough going on every night. You wake up next day, all the pains you never had before. I don't want to go onstage for the sake of the money. You have to have a lot pride in yourself, and I honestly think I'm coming to the end of the top of my job."