He told reporters according to UK Sun that: "We have had proposals from all continents, but my new team will be the Japanese Sagan Tosu".
Chicago Fire are now 7th in MLS' Eastern Conference - a point off of the playoff spots - and Torres would be another big-name addition to the North American league after Wayne Rooney recently joined relegation-threatened DC United.
A World Cup and European championship victor with Spain, Torres made his final appearance for Atletico as a late substitute in Madrid's Europa League final win over Marseille.
Torres, 34, left boyhood club Atletico Madrid at the end of the season following the expiration of his contract and made a decision to depart Europe despite several offers to stay within the continent. Numerous reports indicate that Torres has signed an 18-month contract with options beyond that.
"Sagan Tosu were one of the first clubs to be interested in me, they have convinced me with the project".More news: Protests, pro-rallies planned across United Kingdom ahead of Trump's visit
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"I hope to make my debut, at home, on July 21, then to be there for many years".
"But at no point did I think about moving to another European team".
Sagan Tosu president Minoru Takehara was present at the announcement, posing with Torres as he held the No. 9 shirt he he will wear next season.
Torres is following in the footsteps of his World Cup and European Championship-winning team-mate Andres Iniesta, who recently joined Japanese side Vissel Kobe after leaving Barcelona.
The Spaniard, 34, rejoined his boyhood club in 2014 after a loan at AC Milan.