The University of Otago-trained singer is one of 20 finalists out of 600 singers from 36 countries who auditioned.
The patron of the competition is New Zealand opera singer Dame Kiri Te Kanawa. She succeeded Dame Joan Sutherland, who died last year.
Leese's former vocal coach, University of Otago senior teaching fellow in voice, Isabel Cunningham, said the competition was the most significant in the world for young singers.
"It's huge. It's the launching pad for a career, if you win it," she said yesterday.
"It's the premier showcase for opera and concert singers at the start of their careers. Anyone who wins it is guaranteed a professional career."
While it was still "in the lap of the gods" whether Leese forged a career in opera, she had every chance, Ms Cunningham said.
"She's a very hard worker and has good musicianship."
Leese, who turned 30 on Monday, won the 2001 Otago Daily Times Aria, 2002 Mobil Song Quest, 2004 Royal Overseas League Competition and 2005 Richard Tauber Prize.
She performed last month in the Southern Sinfonia's Last Night of the Proms at the Dunedin Town Hall and the Oamaru Opera House.
The BBC Cardiff World Singer of the Year competition will be held in Cardiff in June.
