The ex-Selecao star slammed Dorival Junior's side in a wide-ranging interview with Brazilian YouTube channel Cartoloucos, just 10 days before Brazil's tournament opener against Costa Rica.

Brazil has not made it past the FIFA World Cup quarter-final stages since 2002, when it won the tournament co-hosted by Japan and Korea Republic Japan, while it finished runner-up at the last Copa America after losing to Argentina in the final.

The South American giant was held to a 1-1 draw with United States in its final warm-up game on Friday (AEST) and Ronaldinho has lost patience with his country's footballing state.

"That's it folks, I've had enough," Ronaldinho posted on Instagram, alongside a clip of his interview on YouTube. "This is a sad moment to enjoy Brazilian soccer.

"It's hard to find the mood to watch the games. This is perhaps the worst time in the last two years, no respected leaders, just average players in their majority.

"I've been following football since I was a kid, long before I thought about becoming a player, and I've never seen a situation as bad as this.

"Lack of love for the shirt, lack of grit and the most important of all: football. I'll repeat, our performance has been one of the worst things I've ever seen.

"Such a shame. I therefore declare my resignation. I will not watch any CONMEBOL Copa America game, nor celebrate any victory."

Brazil faces Paraguay and Colombia in their other group games at the Copa America as it aims for international glory, with or without the backing of its global superstar.