Ronaldinho has told FourFourTwo that he was "48 hours" from signing for Manchester United.
Sir Alex Ferguson targeted the Brazil star after selling David Beckham to Real Madrid in 2003, and United were close to concluding negotiations with Paris Saint-Germain before Barcelona stepped in.
"It almost happened with United," Ronaldinho said.
"It was a matter of 48 hours, but Sandro Rosell had told me way before I got the offer: 'If I become Barca president, will you come?' I said yes.
"It was only a matter of details with United when Rosell called to say he was going to win the elections there.
"And I had promised to him that I'd play for Barca. It was a quick negotiation. I told the English I had chosen Barca."
Ronaldinho won two Spanish titles and the Champions League during his five seasons at Camp Nou.
He left for AC Milan in 2008 and said he did not regret turning down the chance to move to Old Trafford.
"It was the right choice," he added. "Brazilians have always loved Barca. We have a history there.
"Off the pitch it is like nowhere else in Europe, so we are always happy playing there.
"I miss Barcelona a lot. I had five fantastic seasons there, at a club that likes strikers and talented players."