World No.11 Argentinian Juan Martin del Potro is the latest confirmation for the Auckland Classic tennis tournament in Auckland early next year.
Del Potro has captured 20 ATP Tour career titles, including the US Open in 2009, when he became the first player to beat both Rafael Nadal and Roger Federer in the same Grand Slam.
More recently, del Potro knocked Federer out of the US Open in the quarter-finals before narrowly going down to eventual champion Nadal in the semis.
The 29-year-old won silver at last year's Rio Olympics, where he beat world No.1 Novak Djokovic in the first round and Nadal in the semi-final before losing to Andy Murray in the gold medal match.
Del Potro also led Argentina to victory over Croatia in last year's Davis Cup final.
Auckland will be the only tournament de Potro plays before heading to the Australian Open in Melbourne.
He joins a strong field which includes former four-time champion David Ferrer of Spain as well as previous winners in world No.8 Jack Sock and fellow American John Isner (17th), and Spaniard Roberto Bautista-Agut (20th).
The ASB Classic begins with the women's event on January 1-6, before the men are on court from January 8-13.