Spain's top two divisions started a series of meetings this month to discuss the possibility of creating a separate first division similar to the English Premier League, but Del Nido said a number of clubs were at odds with Real and Barca.
"The clubs have to impose on the big two the conditions in play and if they don't accept them, no problem, we will have a league of 18 teams and they will have a magnificent one of two," Del Nido was quoted as saying on the club website.
"This is a cake in which everyone participates and our decision will be radical.
"It is our responsibility to make sure it (the league) doesn't become a fight between only two teams."
Barca pipped Real to the La Liga title last month, both breaking the previous points record for a season with third-placed Valencia a distant 25 points behind Real.
One of the main bones of contention between the top two and the rest is the distribution of television money.
In Spain, clubs negotiate deals with TV companies individually, unlike the Premier League, the German Bundesliga and France's Ligue 1, where collective deals are struck and revenue shared out.
Real and Barca, two of the world's richest clubs, rake in half the available cash with deals worth about 150 million euros a season.
They have repeatedly said they are unwilling to accept a system of collective bargaining, arguing that it would hurt their competitiveness in European competition.
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