Simona Halep said finishing the year at the top of the rankings is "the most important thing" for WTA Finals contenders but plans to put thoughts of remaining number one out of her mind on court in Singapore.
Halep moved to the top of the summit for the first time this month but six of her seven rivals in Singapore could replace her at the season-ending tournament.
The Romanian described usurping Garbine Muguruza to become the best player in the world as the best day of her life and is determined to retain her status next week.
Halep, who faces Caroline Wozniacki in her opening Red Group match on Monday, said: "I think for everyone it is the most important thing to finish the year number, but is not going to be easy.
"Here everyone is going to play the best tennis, and every match is going to be like a final, as I said many times.
"So I'm not thinking about that. I play better when I'm not thinking about number one. I have a lot of experience this year, I'm just going there to give my best, to try to be focused on what I have to play in each match, and we will see at the end who is going to be number one."
Muguruza, named 2017 Singles Player of the Year, spent only a short time as world number one before being replaced by Halep and is relishing the battle for top spot.
The Wimbledon champion, who faces Jelena Ostapenko on Sunday, said: "It is important, I'm not going to lie, of course, but I know I have to play well. I know there are so many girls, players, that have the chance.
"I'm happy that I got it in the past, and now I'm not that nervous or obsessed. I think it's different. So I'm going to fight for that."
Halep will face Elina Svitolina and Caroline Garcia – the only player who cannot go top of the rankings – as well as Wozinacki in the round-robin stage, while Muguruza comes up against Karolina Pliskova, Venus Williams and Ostapenko in the White Group.