Petra Kvitova defeated Caroline Wozniacki in an early-season clash between the world's top two players at the Hopman Cup in Perth.
The Wimbledon champion, who moved up to second in the world last year, won 7-6 (7-4) 3-6 6-4 as the Czech Republic reached the final of the team event.
Kvitova will replace Wozniacki as the world number one if she wins the Sydney International next week.
The pair, both 21, have now won three times each in their six meetings.
"I'm really happy that I won because it was a little test of how we are prepared for the Aussie Open," said Kvitova.
"Caroline played really well. It was a close match, but every match is different and it is not the Aussie Open. I understand that people like seeing numbers one and two in the world playing and I hope it was a good match for them to watch.
"It's the first time we have gone to three sets. I was slow in the second set but I needed to be more aggressive. The key was my serve. That was the key for the whole match."
Wozniacki might be coming under pressure from Kvitova but she remains optimistic about the challenge ahead.
"I'm not feeling any pressure about the ranking," said the Dane, who has yet to win a Grand Slam title.
"I've finished number one for two years in a row and I think that's a great achievement. Very few people have ever done that. I'm playing well and enjoying my tennis and I'm excited a new year is starting.
"It was a great match from both of us. It could have gone either way. I feel like my form is starting to go on the up. All I can do is keep focused and win as many matches and tournaments as possible.
"We have just over a week before the Australian Open starts. I think I've got a lot to look forward to."
In Hobart, Britain's Heather Watson beat Serbia's Bojana Bobusic 3-6 6-3 7-5 in her first match of 2012 in the opening round of qualifying for the Moorilla International, but compatriot Anne Keothavong lost 2-6 6-2 7-5 to Michaella Krajicek of the Netherlands in Sydney qualifying.