As Brazil labours to prepare for next month's World Cup, FIFA secretary general Jerome Valcke got some welcome news ahead of schedule when his daughter was delivered three weeks early.

After years of missed due dates in preparation, the World Cup opens June 12 in Sao Paulo with some of the 12 stadiums largely untested.

"I would not say it's not ready, but it's not finished," Valcke said of the World Cup project at a briefing on Friday.

Valcke's good news came on May 1, when his daughter, Valentina, was born, a rare early arrival during the troubled tournament planning.

"At least she arrived on time, three weeks before, so she's good," the 53-year-old Frenchman quipped with reporters.

The Itaquerao Stadium in Sao Paulo, which will host the Brazil-Croatia opener, has been seen as the symbol of the host nation's much-criticized efforts amid protests that authorities are too focused on football and not the needs of the people.

The venue is late, expensive and within sight of an occupation of private land by thousands of protesters who claim they have been made homeless by rising rents in the neighbourhood.

With 14,000 guests, including invited heads of state, in the 65,000-strong crowd for the opening match, the scrutiny on Sao Paulo will be intense and likely unforgiving.

"This is why we need to have a level of operation which is perfect," Valcke said.

Pressure on FIFA, local organizers and Brazil's infrastructure will not ease during a tough early-match schedule. There is Spain-Netherlands in Salvador and England-Italy in the remote new Manaus arena, quickly followed by Germany-Portugal in Salvador and Brazil-Mexico in Fortaleza.

"These stadiums will be used at 100 per cent of capacity," Valcke said.

Reflecting on seven official years of World Cup work ahead of his May 18 departure to Brazil, Valcke accepted that "many things" could have been done differently.

"It is difficult. Maybe we should have involved the Brazilian government before," he said.

'Social problems in Brazil' 

Valcke said street protests which marred the Confederations Cup last June will likely return during the 31-day, 64-match World Cup. However, political demonstrations and banners will not be allowed inside stadiums.

He said it was "naive" to think Brazilian people would remain calm for as long as their team stays in the competition.

"It goes beyond that," he said. "Reasons for being in the streets in 2013 have not changed.

"There are social problems in Brazil. It will take time."

While the 2014 World Cup will certainly be a commercial success for FIFA, Valcke has concerns for fans who clamoured for tickets in record numbers.

"I think that the biggest challenges will be for them," he said. "It will not be for the teams, it will not be for the officials."