JOHANNESBURG — World Cup organizers say 500,000 tickets are unsold and fear "tragic" empty stadiums at football's showcase event.

FIFA said Friday the tickets would go on sale to the general public in South Africa from April 15. Organizers have less than two months to sell nearly a quarter of the tournament's total match tickets to avoid empty seats.

Organizers conceded their online process was not suited to local fans, who are generally poor and not used to buying tickets on the Internet.

FIFA secretary general Jerome Valcke says "there is always time to learn."

Organizing committee chief Danny Jordaan says it would be "tragic" for the host country if stadiums were empty and urged fans to "go buy now."