The top 10 in the rankings remains unchanged but Kerber, just 190 points behind the American, is hoping to alter that at the last grand slam of the season starting in New York.
Kerber had a chance earlier this month to unseat Williams at the Cincinnati Open but lost in a shock final defeat to Czech Karolina Pliskova.
WTA rankings
1. Serena Williams (USA) 7,050 pts
2. Angelique Kerber (GER) 6,860
3. Garbiñe Muguruza (ESP) 5,830
4. Agnieszka Radwanska (POL) 5,705
5. Simona Halep (ROM) 5,151
6. Venus Williams (USA) 4,005
7. Victoria Azarenka (BLR) 3,551
8. Roberta Vinci (ITA) 3,465
9. Madison Keys (USA) 3,286
10. Svetlana Kuznetsova (RUS) 3,190
11. Karolína Plísková (CZE) 3,135
12. Carla Suárez (ESP) 3,100
13. Dominika Cibulková (SVK) 3,100
14. Johanna Konta (GBR) 2,905
15. Timea Bacsinszky (SUI) 2,713 (+1)
16. Petra Kvitová (CZE) 2,580 (-1)
17. Samantha Stosur (AUS) 2,370
18. Anastasia Pavlyuchenkova (RUS) 2,195
19. Elina Svitolina (UKR) 2,101 (+4)
20. Elena Vesnina (RUS) 2,054