Organizers of the World Cup are in a race to get ready, and the biggest challenge with three months to go is to install all the temporary structures needed for matches in Brazil's 12 host cities, FIFA's secretary general said Thursday.

Jerome Valcke told the cities will have "to race" to get stadiums, other facilities and infrastructure done in time for soccer's premiere event.

Brazilian organizers had promised to finish all stadiums by the end of last year but only six were ready. Three still aren't finished, including the one in Sao Paulo that is to host the opening match between Brazil and Croatia on June 12.

"It's not just FIFA being in a race," Valcke said. "It's the local organizing committee, the government and the host cities which have still to run and to race."

Temporary structures still need to be installed outside stadiums for the media, sponsors and technical teams.

"The biggest challenge is to make sure that all what we call these temporary facilities can be in place," Valcke said.