Sania Mirza and Martina Hingis beat Taiwan's Hao-Ching Chan and Yung Jan Chan 7-6 (12-10), 7-5 to enter the semifinals of the WTA Finals Singapore on Friday.
They will face the winner of the match between top seeds Caroline Garcia-Kristina Mladenovic and Bethanie Mattek-Sands- Lucie Safarova, who are set to play later in the day.
Both pair held their serves in the first ten games, and Sania-Hingis were the first to be broken in the 11th. But they broke back in the following game to make it 6-6. The tie-breaker was tightly fought, and the Indo-Swiss pair saved three set points. They dropped two set points of their own, but held on to their third to take the first set in just over an hour.
The second set was similarly tight as both pairs lost two serves each by the eighth game. At 5-5, Sania-Hingis secured a crucial break and then held their serve on the next one to book a place in the last four.
This is Sania and Hingis' first competition since their reunion. They had split following an early exit at Montreal in July, but had assured themselves of a place in the elite field of eight teams by continuing their sparkling run from 2015 into the early phase of this year.
Mirza, who has been ranked number one for 80 weeks, can be displaced if she fails to win the event.
"Even if I lose the number one ranking, that's not going to change anything. I will just be inspired to come back and work harder," Mirza had told ESPN before the tournament.