The tournament to be held at the Buenos Aires Lawn Tennis Club from Feb. 10 to 16 is part of the Latin American swing of claycourt events which also includes tournaments in Chile, Brazil and Mexico.
"After a time when I was unable to go, this year I'm going to return to the Buenos Aires tournament and I'm excited to play the Copa Claro again," Nadal said in a video shown at a news conference.
Nadal lost to Argentine Gaston Gaudio, the 2004 French Open champion, in the quarter-final of the 2005 Buenos Aires tournament at the start of a glittering career that has included 13 grand slam titles, eight at Roland Garros.
"We're very happy to have Rafa, to have a world number one playing for the points in Argentina," said tournament director Martin Jaite, who is also his country's Davis Cup captain.
Nadal made his comeback from a long injury layoff at the Vina del Mar tournament in Chile last February, launching a comeback that took him back to the top of the rankings last month.
He was in Argentina last month for exhibition matches against world number two Novak Djokovic and retired Argentine former number three David Nalbandian's farewell to tennis.
Buenos Aires champion David Ferrer will not be defending his title.
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