Sabalenka retained the Australian Open title in January, lifted the US Open trophy and triumphed in Cincinnati and Wuhan to leapfrog Swiatek and top the WTA rankings last month.
Iga Swiatek is out to retain her Finals trophy in Saudi Arabia. (AP PHOTO)
Five-times grand slam champion Swiatek made a strong start to the season and has bagged five titles, including her fourth French Open crown, but the 23-year-old from Poland ran out of steam and skipped the recent Asian swing through fatigue.
The pair are the only players to hold the No.1 ranking since April 2022 and will battle hard for year-end glory and more than a third of the $US15 million ($A23 million) prize pot in the capital Riyadh.
"Yeah, that's definitely one of the goals," said Sabalenka.
"I've always been saying that for me it's about finishing the year as the world number one. I'll do everything I can.
"Any time we come to the tournament, we want to win. That's the first goal. I'm trying to be focused on the first part. Then, if I'll be able to finish the year as number one, it'll be amazing and I'll be super happy."
The 26-year-old was in a similar position last season when she arrived at the WTA Finals in Cancun, Mexico, needing to fend off Swiatek to finish on top but the Belarusian was unsuccessful in her bid.
Winning three round-robin matches or reaching the final are some of the ways Sabalenka can retain top spot this year, while Swiatek needs to successfully defend the trophy to have any chance of overtaking her.
"Obviously we're both fighting for this spot. It's been us basically, over the past few years," Swiatek said.
"I'm in the tournament. I want to play my best and win. I'm going to focus on my first match and do everything step by step.
"She's a great player. She also deserves to be number one. For sure, I'm going to fight for me to be in that place."
Looking to make life difficult for the duo are Zheng Qinwen, Jasmine Paolini, Jessica Pegula, Coco Gauff, Elena Rybakina and Barbora Krejcikova.
The Finals, which run for a week from Saturday, have been the subject of intense debate in the last few months after Riyadh won the right to host the event until 2026.
Saudi Arabia has invested heavily in sports like soccer, Formula One and golf in the last few years while critics accuse the kingdom of using its Public Investment Fund to "sportswash" its human rights record.
WTA chief Steve Simon said last year that Saudi Arabia presented "big issues" as a host for women's tour events, but also acknowledged the progress it had made and continued to engage with players before the WTA Finals deal was struck.
