On a day when a transport workers’ 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.