The 28-year-old is one of coach Dunga's over-age players for the Olympics after his new club AC Milan gave the go-ahead for him to take part.
He said he was feeeling fit and finding his best form. "Even though I haven't played important international matches for four months, I have been training really hard and I am in good condition," the two-time FIFA World Player of the Year told a press conference here.
Ronaldinho scored 70 goals in 145 appearances for Barcelona, helping them win the Spanish championship in 2005 and 2006 as well as the 2006 Champions League.
But after a dip in form last season, attributed by some to his penchant for late-night partying, he was deemed surplus to requirements and AC Milan signed him for an estimated 30 million dollars. He said he was looking forward to a new start.
"I feel happy to transfer to AC Milan. I am a professional footballer, every transfer is a new start for me," Ronaldinho said. "But for the moment the most important thing is the Olympics. It's a great honour to represent Brazil in the Games.
"My goal is to create history for Brazil. The Olympics is as important as the World Cup and Copa America, everybody wants to be the champion in the Olympic games," he added.
Despite winning five FIFA World Cups, when it comes to the Olympics Brazil have been found wanting with runner-up finishes in 1984 and 1988 and a bronze medal in 1996. Brazil open their Olympic campaign here on Thursday against Belgium. New Zealand and hosts China are also in their pool.