Football supremo Sepp Blatter voiced confidence on Thursday that Brazil would deliver a successful World Cup, as the city hosting the tournament's opening match grappled with transport chaos.
Speaking in Sao Paulo just one week before the World Cup kicks off in the sprawling city, FIFA president Blatter predicted tensions threatening the tournament would subside once the football began.
"We at FIFA, we are confident, it will be a celebration," Blatter said. "I'm an optimist. After the tournament kicks off I think there will be a better mood."
FIFA secretary general Jerome Valcke insisted preparations were on track but acknowledged the opening weeks of the tournament would be the "most challenging."
"We are in control, we have nothing to fear in the coming days," Valcke said.
The assurances were at odds with the chaos gripping Sao Paulo on Thursday, however, as subway workers went on strike in the Brazilian economic capital.
The Sao Paulo metro is the main link to the city's stadium, and the strike could pose a logistical headache for cup organizers -- as well as the 4.5 million passengers who use the system daily.
Frustrated commuters broke entrance grilles at the station that serves the World Cup stadium, Corinthians Arena.
After some of them jumped onto the tracks, system operators CPTM decided to open the station in a bid to calm the situation.
With more people using their cars, bumper-to-bumper traffic stretched for up to 209 kilometers (135 miles) during the morning rush-hour, the worst congestion so far this year and the third worst ever recorded in the sprawling city of 20 million people.
Another strike by 75 percent of Sao Paulo's traffic police exacerbated transport problems.
The subway strike affected three of the city's five metro lines, a system employee told AFP.
Sao Paulo was where mass protests erupted a year ago as citizens took to the streets to voice anger at rising public transport fares.
The unrest ballooned into nationwide demonstrations against the more than $11 billion being spent on the World Cup.
During the Confederations Cup, a World Cup dress rehearsal, protests drew a million people into the streets -- at times turning violent and overshadowing the tournament
Amnesty International said the police response to the protests had been characterized by violence and abuses, and warned Brazil against cracking down on demonstrations during the World Cup.
"Brazil's deficient policing record, reliance on the military to police demonstrations, lack of training and an atmosphere of impunity creates a dangerous cocktail," said Atila Roque, Amnesty's country director for Brazil.
- Unfinished stadiums -
The protest movement has lost momentum since last June, but Thursday's transportation chaos risks rekindling anger with one week to go to the opening ceremony.
"People were fighting to get onto the train," commuter Edith Carvalho, 40, told AFP.
Workers went on strike at midnight after negotiations on a salary increase fell through. They rejected an offer of 8.7 percent, insisting on at least 10 percent.
Talks between union leaders and subway management ended on Thursday with no deal.
President Dilma Rousseff has defended her government's preparations, insisting the money spent will leave a legacy of airports and transport infrastructure that will benefit Brazil for years to come.
But the government has also faced criticism for chronic delays and disorganization.
Workers are still scrambling to finish several of the 12 host stadiums, including Corinthians Arena, which has not received safety clearance from firefighters to operate at full capacity.
Eight workers died in construction accidents at the stadiums, including three in Sao Paulo.
Much of the other promised infrastructure has been shelved, from roadworks and a high-speed train to subway and monorail lines.
Meanwhile, teams continue trickling into Brazil. Chile's arrival on Thursday followed Australia, Croatia and Iran.
Brazil, who routed Panama 4-0 in a friendly on Tuesday, play Serbia on Friday in a final warm-up before next week's tournament opener against Croatia.