On a day when a transport workers's strike brought part of Brazil's biggest city to a halt, Brazil's Sports Minister said it was impossible to promise his country would be ready for next week's opening match of the World Cup.

"When you are dealing with an event as big as the World Cup there is no way for you to put a diploma on the wall saying you are ready," Aldo Rebelo told reporters in Sao Paulo.

"You have to be prepared every day," the normally upbeat Rebelo added. "Everything needs to be working 24 hours. I am not going to hang a diploma on my wall and say 'Here is my diploma, everything is ready.' We have done everything within our capacity so that things are as close as possible to ready."

Large parts of Sao Paulo came to a standstill on Thursday after a strike by metro workers prompted people to take their cars to work. It was the latest in a series of stoppages to hit Brazil in recent weeks.

Police, teachers and bus drivers have also been on strike in search of higher wages, causing fears that the tournament, which kicks off next Thursday when the host nation faces Croatia, could be affected.

However, the 12 stadiums should be ready, even though workers are still putting the finishing touches to some of them, Jerome Valcke, FIFA's secretary general, said.

Valcke acknowledged some stadiums are still fitting seats and others are installing generators, amongst other issues.

"It looks like there is quite a lot of work going on," said Valcke. "I would say that is quite normal. And that is more normal when you consider the stadiums were delivered late.

"We are not afraid of the next days."

FIFA President Joseph Blatter dodged the elephant in the room by sidestepping questions over Qatar, the hosts of the 2022 World Cup. Allegations have surfaced that money was paid to influence the decision, but Blatter said he would not address the issue until investigator Michael Garcia finished his enquiry.

"The only thing I can say to the Qataris is that in March this year we said we don't put the World Cup in Qatar into question and we are waiting the result of the investigation," Blatter said. "I am not a prophet, so we await the results and see what happens."

Blatter, who has indicated he will seek another term as FIFA president in 2015, also refused to take a stand on possible term limits. He said the Executive Committee meeting scheduled for next week in Sao Paulo might vote on the issue.

"My opinion is that we have already had this on the agenda in Mauritius and the congress said we will deal with it in Sao Paulo," Blatter said. "So let them deal with it."