Britney Spears

'N Sync and Britney Spears are set to follow in the footsteps of Guns N' Roses and Queen by performing at the third Rock in Rio for a Better World

festival Jan. 12-21, 2001 in Rio de Janeiro.

The teen acts will headline a

bill that features ninety-six other artists. Organizers are expecting a

crowd of 1.5 million, with five percent of the proceeds going to charity.

The debut Rock in Rio festival, held in 1985, attracted 1.38 million people,

while the last, in 1991, drew 700,000. Tickets go on sale in October.