Second seed and US Open finalist Caroline Wozniacki outplayed Garbine Muguruza 6-4, 2-6, 6-2 on Saturday to reach the final of the $US1 million ($A1.08 million) WTA Pan Pacific Open in Tokyo.

The 24-year-old Dane, playing in her first tournament since losing to world No.1 Serena Williams at Flushing Meadows two weeks ago, broke the Spaniard’s serve five times but lost hers four times in a two-and-half hour marathon.

The 2010 Pan Pacific Open winner will now face top-seeded Angelique Kerber of Germany or third ranked Ana Ivanovic of Serbia in Sunday’s final.

“It was a very tough match. Garbine plays well. I’ve lost to her two times,” Wozniacki said.

“I knew it was going to be very difficult but I am pleased to be through to the next round,” she added.

“It’s been a great week so I want to finish it off on a high.”

Muguruza, aged 20 and ranked 26th, beat Wozniacki in their two previous encounters, taking an Australian Open round of 32 clash 4-6, 7-5, 6-3 in January.

Wozniacki broke the Spaniard’s serve in the 10th game to take the first set after surviving nine break points on her own serve.

But she lost her serve three times in the second set, barely holding herself up against six break points in the sixth game.

Wozniacki lost the first two games in the decisive set.

But she rallied back to 2-2 when Muguruza double-faulted and banged a backhand cross-court shot wide after the fourth deuce.

Wozniacki took the next four straight games as an increasingly erratic Muguruza served and shot a forehand wide on match point.

Wozniacki, whose 22 career WTA tiles include the low-tier Istanbul Cup so far this year, ranked as the world No.1 in 2010 and 2011.