Football's international governing body FIFA does not know how many seats are available for this summer's World Cup tournament because of Brazil's failure to meet stadium construction deadlines.
The organisation's marketing director, Thierry Weil, said at a news conference in Rio de Janeiro on Thursday that seven per cent of tickets were being held back.
"We can't say exactly how many tickets there will be because we don't know the exact number of seats in the stadiums.We have held back 7 percent of the tickets until we really know how many tickets will be available."
FIFA wanted the 12 World Cup venues to be finished by last December, but only six were ready by that deadline. Of the remaining six, three remain incomplete, Reuters news agency reported.
Brazil has had seven years to prepare for the tournament but is still trying to finish stadiums, airports, roads and other infrastructure.
Passengers will arrive in a tarpaulin terminal building in at least one airport and several cities have either scaled back plans to build roads, bus lines and railways or shelved the original plans altogether.
The biggest concern for FIFA is the stadiums, particularly the Arena Corinthians, which is scheduled to host the opening match between Brazil and Croatia on June 12. It was built to hold 48,000 people but about 20,000 temporary seats are being added for the tournament's six games and they are still under construction.
Stadiums in Curitiba and Cuiaba are also unfinished and about 27,000 seats are yet to be installed in Curitiba.
Another FIFA worry is the limited amount of time to test stadia facilities.
"At some point in May more tickets will go on sale with the completion of the stadiums," Weil said. "It's just taking time."
"We need to test everything, the communications, lights, cables, all the things that need to work and unfortunately we
can't do that in these stadiums.
"We'd love to test these kind of things and then have time to react to any problems but we'll have to accelerate the process."
FIFA has so far sold more than 2.7 million tickets for the 64 matches, with more than half of them being bought by fans in the host country.