Jessica Pegula beat US Open champion Coco Gauff 6-2 6-1 on Saturday to reach the title match at the WTA Finals in Cancun, Mexico, where she will next face either world number one Aryna Sabalenka or Iga Swiatek.

In the first all-American semi-final at the WTA Finals since the reintroduction of the round-robin format in 2003, Pegula converted six of her 10 break point chances and lost serve just once during the 60-minute encounter.

Pegula broke at love to open the match and attacked her good friend Gauff’s serve twice more for a 5-2 lead en route to taking the first set in comfortable fashion.

In the second set, Pegula again started with a break to love and consolidated for a 2-0 lead before rain halted play for 14 minutes, an interruption during which the wind destroyed the umbrella Gauff was holding over her head.

When play resumed, Pegula remained in control as she added another break to open a 4-1 lead before rain again interrupted play, this time for 13 minutes.

Gauff tried to make the necessary adjustments, but Pegula was rock-solid at the baseline and sealed the win on her second match point to reach the biggest final of her career.

Pegula powers into WTA Finals last four

In the other semi-final, Swiatek faced top seed Sabalenka of Belarus, with the Pole leading 2-1 in the first set before the match, which could decide the year-end world number one ranking, was cancelled for the night due to rain.

The match was called off until Sunday.

If Sabalenka wins the season-ending tournament, she will finish the year as world number one, whereas world number two and four-time major winner Swiatek would need to win the title to retake the top spot from the Australian Open champion.