Opening fixtures to the new La Liga season are in doubt after players voted in favour of strike action over wages.
The dispute is over players' demands for wages to be paid regardless of whether clubs go into administration.
"We are unanimous in our decision," players' union president Luis Rubiales said. "The league will not start until a new agreement has been signed."
"Players from the first and second divisions have made the decision to call a strike for the first two match days of the season.
"The players have met with us and decided that enough is enough," he added.
A similar disagreement over television money threatened to delay the start of last season, but the situation was resolved in time for the opening day.