SAO PAULO - A Brazilian court rules Sunday on the legality of a subway strike threatening to disrupt the World Cup's opening game with just four days until kick-off in Sao Paulo. The strike has brought traffic mayhem to the business hub of 20 million people as it prepares to welcome more than 60,000 fans for Thursday's game between Brazil and Croatia. The subway workers' union awaited a ruling by a regional court but warned it could continue the work-stoppage regardless of the legal battle's outcome.The strike over wage demands is the latest social upheaval to hit Brazil, where protesters angry at the World Cup's $11 billion bill have staged demonstrations. The five-line system was partially operating, but subway trains were not arriving at the Corinthians Arena that will host the opening game. Subway union official Rogerio Malaquias told AFP that up to 95 percent of employees support the strike."As long as there is momentum, the movement will continue and could continue until the World Cup," Malaquias warned. Union workers have reduced an initial claim for a 16.5 percent wage hike to 12.2 percent, but employers are offering only 8.7 percent. The subway standoff led to a clash Friday between picketing strikers and police inside a metro station, with authorities swinging truncheons and firing tear gas to disperse the protesters.Authorities are hard-pressed to resolve the latest labor dispute to avoid another embarrassing incident in a World Cup hit by delays even before it has started. The Corinthians Arena has itself been plagued by delays, and construction workers were racing against the clock over the weekend to finish it before the opening whistle: wiping seats, checking beams and installing wiring in two temporary stands."There's still much to do," said one worker, who spoke on condition of anonymity because he was not authorized to speak to the media. Another used his sleeve to wipe sweat away from his forehead as he said: "It will be ready before the World Cup." Delays at five of the 12 World Cup stadiums have contributed to the rising bill of hosting the tournament, infuriating many Brazilians who have held protests demanding President Dilma Rousseff spend the money on hospitals and education instead.Rousseff charged that the protests were orchestrated to derail her Workers Party (PT) before October 5 general elections. "Today, there is a systematic campaign against the World Cup -- or rather, it is not against the World Cup but rather a systematic campaign against us," Rousseff said late Friday in the southern city of Porto Alegre. Rousseff, a leftist political prisoner during the 1964-1985 military dictatorship, said that even in the days when the likes of Pele were leading Brazil to glory, "we did not confuse the World Cup with politics."The president insists the money spent on the tournament will leave a legacy of modernized airports and transport infrastructure that will benefit Brazil for years to come. But much of the other promised train and road infrastructure has been shelved, while five of the 12 stadiums have yet to be finished. Last year's Confederations Cup, a World Cup dress rehearsal, saw more than a million people take to the streets, but this year's demonstrations have been smaller.