Lars Ulrich of Metallica performing a special album lunch concert at the O2 Arena, London, England - 15.09.08

The rock star insists the group has no plans to split in the near future, but touring will become a problem if he can no longer keep up.

He tells Rolling Stone magazine, "The Rolling Stones, Black Sabbath, Aerosmith, I have nothing but respect for their longevity but (Stones drummer) Charlie Watts isn't playing Damage, Inc. three times a week or playing Whiplash every night.

"This (Metallica) has the potential to go on for a long time. But if somebody's arm, back or neck just says, 'F**k this,' and quits, I don't know..."

Source: WENN