Brazil approved a law Monday creating 20 percent quotas for mixed race and black Brazilians in government jobs, in a country where more than half of the population has African roots.

"We have started this change in the racial composition of public officials in the federal administration so it will be more representative of the Brazilian population," said President Dilma Rousseff during a ceremony for the enactment of the law.

The World Cup kicks off Thursday and soccer fans from Rio de Janeiro's slums to southern India's playgrounds have been shining with their passion for the sport.

While national teams are arriving in Brazil, some in Latin America have set out to travel in the most unconventional ways to witness what they describe as a once-in-a-lifetime event. Some Chilean soccer fans built a wood-framed trailer from scratch to travel together and save money on lodging and meals.

Brazil's World Cup preparations endured a rough Friday, as police clashed with striking subway workers in Sao Paulo, massive traffic jams snarled the mega-city and fans booed the national team.

The scuffle in the metro station and a separate anti-government protest that gathered 3,000 people raised fears of more unrest when Brazil and Croatia open the World Cup in Sao Paulo on Thursday.

Subway workers in Sao Paulo went on strike Thursday, one week before the World Cup opens in the Brazilian mega-city, where protests against government spending on the tournament erupted a year ago.

The Sao Paulo metro is the main transport link to the economic capital's World Cup host stadium, and the indefinite strike could pose a massive logistical headache for organizers.

Brazil is to deploy a 170,000-strong security force for the World Cup to deter hooligans from home and abroad.

Mass protests against the tournament and deadly fan violence have put authorities on alert ahead of the start of the tournament on June 12.

Brazil said Friday it is mobilizing 157,000 soldiers and police to ensure security during the World Cup, which opens in 20 days against a backdrop of violent protests and strikes.

The defense ministry said it would provide 57,000 navy, army and air force personnel for the event, including 21,000 who will be on a state of alert for situations requiring immediate intervention.

One of Brazil's top Catholic bishops has spoken out in favor of legal unions for homosexual couples, an apparent shift in the Church's stance on the country's existing gay-marriage policy.

"There needs to be a dialog on the rights attached to shared life between people of the same sex who decide to live together. They need legal support from society," Leonardo Steiner, the secretary general of the National Confederation of Brazilian Bishops, said in an interview with O Globo newspaper published on its website Thursday.

Dozens of protesters clashed with police late Friday, throwing fireworks and torching at least two vehicles near Sao Paulo's airport, which has just opened a new international terminal ahead of the World Cup.

Police responded with stun grenades to disperse the estimated 50 protesters who demonstrated in the Sao Paulo suburb of Guarulhos to demand better living conditions, according to media reports.

The cost of building Brasilia's World Cup stadium has nearly tripled to $900 million in public funds, largely due to allegedly fraudulent billing, government auditors say. The spike in costs has made it the world's second-most expensive soccer arena, even though the city has no major professional team.

Now, an Associated Press analysis of data from Brazil's top electoral court shows skyrocketing campaign contributions by companies that have won the most World Cup projects. The lead builder of Brasilia's stadium increased its political donations 500-fold in the most recent election.

President Dilma Rousseff faces a tough re-election campaign after being chosen as the left-wing Worker's Party's candidate for the October presidential election.

Rousseff's re-election bid was formalized at a raucous party event late Friday and fully endorsed by party stalwart and popular ex-president Luiz Inacio Lula da Silva (2003-2011).