Ronaldo was given a stern warning by Brazil coach Carlos Alberto Parreira on Friday after saying that he wanted to be excused from playing in the Confederations Cup because he needed a rest.
"He has the right to ask to be excused and if there's a very good reason we will have a look," said Parreira. "But if he asks to have a rest, I won't accept it, that excuse doesn't exist."
"It would be great just to play the World Cup," added Parreira, who spoke at Rio de Janeiro airport after returning from Turkey where he watched Wednesday's European Champions League final.
"Personally, it would be great for me if I could just coach the team at the World Cup and not have to worry about the qualifiers and the friendlies where there is a lot of wear and tear."
Parreira added: "Nobody is irreplaceable and they're quite welcome to stay at home if they don't want to play -- in fact it's better if they stay at home because otherwise they'll just get in the way of the others."
Parreira, who said earlier this month that holidays were "relative", has named a full-strength squad for the June 15-29 eight-nation competition to be held in Germany. He wants to use it as a try-out for next year's World Cup.
Brazil have already rejected requests from Real Madrid, Barcelona and Inter Milan to excuse Ronaldo, Ronaldinho and Adriano respectively.
Ronaldo, who was allowed to skip last year's Copa America in Peru, gave a newspaper interview earlier this week playing down the importance of the tournament and saying he needed a rest.
The other teams at the Cup are hosts Germany, Australia, Argentina, Tunisia, Greece, Japan and Mexico.
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