Ground staff at Rio de Janeiro's airports have called a 24-hour partial strike Thursday, the day Brazil hosts the opening match of the World Cup.
The workers vowed to respect a court ruling ordering them to maintain 70 to 80 percent service, but the strike will nevertheless raise fears of delays as thousands of football fans descend on the tourist-magnet city around the opening match in Sao Paulo and first game in Rio on Sunday.
"We're Brazilian and we continue to root for Brazil, but it's our duty to fight for workers' rights," union president Rui Pessoa told AFP.
The union is calling for World Cup bonuses, better working conditions and raises of up to 12 percent, but says employers are offering a maximum of eight percent.
The strike comes after "nine months of intense but failed negotiations and intransigence from employers," the union said on its website.
The walkout, which starts at midnight (0300 GMT), will affect the city's two main airports, Galeao International and Santos Dumont, which handles domestic flights.
A court ordered airline employees to maintain at least 70 percent service and employees at other companies to maintain at least 80 percent service.
The National Civil Aviation Agency said it was monitoring the situation and had contingency plans in place for World Cup strikes.
Pessoa said that although the strike was only partial he believed it would have "consequences" because of the increased number of flights during the World Cup -- more than 1,000 a day in Rio.
Rio is one of the major arrival points for foreigners visiting Brazil.
It is a 40-minute flight from Sao Paulo, which hosts Thursday's opening match between Brazil and Croatia.
More than three million Brazilians and 600,000 foreigners are expected to criss-cross Brazil during the tournament, which wraps up with the final match in Rio on July 13.