Victoria Azarenka of Belarus celebrates defeating Svetlana Kuznetsova of Russia in their women's singles quarter-final match at the Australian Open tennis tournament in Melbourne.

Melbourne - Defending champion Victoria Azarenka overcame a stubborn Svetlana Kuznetsova 7-5, 6-1 on Wednesday to advance to the Australian Open semi-finals.

The world number one, who apart from a short period against an injury-hampered Jamie Hampton in the third round, had been barely tested in her title defence until she ran into the two-times grand slam champion in the quarter-finals.

Kuznetsova competed in the longest women's game at the Australian Open when she lost a marathon four hour, 44 minute clash 6-4, 1-6, 16-14 to Francesca Schiavone in 2011, and it looked like she was prepared to exceed that after a marathon 77-minute first set.

Azarenka, however, decided that she had enough of the Russian keeping her on court and raced through the second set in 30 minutes to set up semi-final against either third-seed Serena Williams or Sloane Stephens. - Reuters