Serena Williams survived a testing examination from fellow American Sloane Stephens at the Brisbane International on Thursday to book a semi-final against world number one Victoria Azarenka.
Williams was pushed all the way by her Fed Cup teammate in the last of the four quarter-finals before winning 6-4, 6-3 in 71 minutes in Pat Rafter Arena.
Earlier Azarenka, of Belarus, swept aside the challenge of Kazakhstan qualifier Ksenia Pervak 6-1, 6-0 in her most impressive display of the tournament.
Williams and Azarenka have met 12 times previously, with Williams winning all but one of those encounters.
Friday's clash will be a tantalising warm-up for this month's Australian Open, where there is a strong possibility the two women will meet in either the semi-finals or final.
"I'm going up against the best player in the world," Williams said. "She's had a fabulous year, she won the Australian Open and has been the most consistent all year.
"I've got nothing to lose. I can go out there and see where my game is at."
Williams, 31, has hardly been pushed this week and was expected to waltz through her clash with 19-year-old Stephens in their first ever meeting.
But Stephens matched the world number three shot for shot, often leaving Williams stranded on the baseline with the power and accuracy of her groundstrokes.
Stephens attacked Williams' serve and had the first opportunity to break but couldn't convert. Williams then took her only break point to win the set.
The second set was almost a carbon copy of the first, this time with Williams breaking at 4-3, before holding to love to claim a highly entertaining match.
"I think she can be the best player in the world one day," Williams said later.
Azarenka was in superb form as she crushed Pervak, who had upset former world number one Caroline Wozniacki in the first round.
"It was pretty good, even though we had some tough games I felt I was playing really well at the important moments and taking my chances to close out the games," she said.
She said she was excited about the prospect of playing Williams.
"It's a tough match, there is no question about it," she said. "I'm looking forward to it. There is one more chance for us to meet (before Melbourne) and it's going to be a great test for the Australian Open.
"I'm not looking for easy matches. The tougher it is the more exciting for me it's going to be, so I'm quite happy with that."
The second semi-final will be between two unseeded players after Lesia Tsurenko of Ukraine beat 2012 runner-up Daniela Hantuchova 6-3, 6-4 and Russia's Anastasia Pavlyuchenkova downed fourth seeded German Angelique Kerber 7-6 (7/3), 7-6 (7/3).
The win over Kerber was the powerful Pavlyuchenkova's second defeat of a top 10 player in two days, following her second-round win over Petra Kvitova.
Tsurenko, who lost in qualifying, only made it into the tournament after second seed Maria Sharapova pulled out injured on the eve of the competition.
"I'm just enjoying it now. This is my chance, and I'm taking it," she said .