FIFA is set to meet Tuesday to appoint a prosecutor who will be urged to investigate possible corruption in the votes to decide the hosts for the 2018 and 2022 World Cups.

FIFA's top anti-corruption adviser, Mark Pieth, tells The Associated Press this is ''absolutely fundamental'' if soccer's scandal-hit governing body is to be modernized.

Pieth's panel says the ethics officials must have the authority to examine old cases after finding that FIFA ''insufficiently investigated'' some allegations about World Cup bidding.

Russia won the rights to the 2018 World Cup. Qatar was selected for 2022 ahead of the U.S in a final round of voting.

There have been claims some voters received payments or sought favors from bidders, and several breached rules by joining a pact to back Qatar and the Spain-Portugal bid.