Workers at the grand Maracana football stadium in Rio -- Brazil's largest and the centerpiece of the 2014 World Cup -- said Tuesday they would continue indefinitely a strike that has already halted work for 13 days. The stoppage, the second in just over a month, was backed by the 2,300 workers on the $660 million-revamp for the stadium, who are demanding a health plan, improvement to their food service, and boosted safety controls. The action compounds concerns voiced by world soccer body FIFA over what it says is a slow pace of building ahead of the World Cup. Brazil's President Dilma Rousseff said late last month that preparations for the competition, along with construction around the 2016 Olympic Games, are going ahead at an "adequate pace," promising that nine of 10 stadiums would be likely finished next year. But the labor action in Rio has been echoed by workers in cities around the country, including Belo Horizonte in the southeast and Salvador de Bahia in the northeast. Union leader Nilson Duarte told AFP that "the strike is indefinite," and urged the consortium formed by construction giants Odebrecht, Delta Construcciones and Andrade Gutierrez to return to talks. "If they want to end this situation as quickly as possible, they have to sit down and negotiate," said Duarte. "Our aim is to work, but we cannot continue like his," he added. The consortium said in a statement it saw "no reason for the current stalemate," but union officials said a health plan that the companies said would be provided for each worker had not been made available. The companies said the paperwork for the health plan, due on September 1, had been delayed because the workers were on strike.