SAO PAULO (AP) ― Workers building and renovating Brazil’s stadiums for the 2014 World Cup are threatening to go on strike if employers don’t agree to their demands for unified salaries and benefits.

There have been isolated strikes across the nation, but unions representing the workers in each of the 12 host cities are trying to come together to plead for better conditions.

Union leader Claudio da Silva Gomes said Tuesday the workers are ready to go on strike as early as next month if construction companies don’t agree to give employees the same salaries and benefits regardless of the venue.

FIFA has said World Cup preparations are behind schedule, and stadium construction has been one of the main concerns. The strike would likely create even more delays at several venues, especially the ones to be used for the Confederations Cup next year.

“We have workers doing almost exactly the same kind of work but they are not earning the same salary or being entitled to the same benefits at the different venues. This doesn’t make sense,” said Gomes, a leader at the national union organization CUT. “If they are doing the same work, they should be getting paid the same salary, regardless of which region they are working in.”

He said there are different salaries and benefits to workers even when the same construction company is involved.

Pay discrepancies are common in Brazil in nearly all sectors, especially in the more impoverished north and northeast regions. Gomes said workers in the southeast and the southern regions are making nearly twice as much as the ones in the northeast.

“It’s going to be more difficult to reach an agreement in these areas because the difference between what workers are making there compared to those in the south is significant,” he said.

Support in the cities where workers receive better salaries may not be as strong. Workers in Rio, for example, said they might not join the movement if they are able reach a separate agreement locally.

“We might participate only in solidarity,” Rio de Janeiro union leader Nilson Duarte said. “Or if our agreement is not as good as the one being sought collectively, but we don’t know yet if that’s going to happen.”

There are more than 20,000 workers either renovating or building the stadiums in the 12 host cities.