Teenager Amanda Anisimova upset top seed Zhang Shuai 7-6 (7-4) 7-5 at the Japan Women's Open to reach her maiden WTA Tour final.

Qualifier Anisimova, who only turned 17 a fortnight ago, was twice disrupted by rain delays in Hiroshima but nothing could dampen her spirits in a high-quality show.

Anisimova had 25 winners to just 19 unforced errors in a performance that belied her youth and she now has a 12-3 win record since returning from a foot fracture sustained in March that saw her miss the clay and grass-court seasons.

She becomes the youngest finalist since Donna Vekic played the final of Birmingham as a 16-year-old five years ago.

Hsieh Su-wei awaits in the final after she won two matches to punch her ticket to the showpiece match.

Having beaten Ajla Tomljanovic in three sets in a quarter-final held over from Friday, Hsieh was a 6-4 6-4 victor over Wang Qiang.