Unheralded American Sofia Kenin stunned world number one Ashleigh Barty to end home hopes at the Australian Open on Thursday.

Barty had sent Australian expectations soaring of a first home-grown winner since 1978, but they came crashing to earth against the aggressive 14th seed, who saved two set points in each set to win 7-6 (8/6), 7-5.

Moscow-born Kenin, 21, looked stunned at reaching her first Grand Slam final, at a tournament where she has often gone unnoticed while fellow Americans Serena Williams and 15-year-old Coco Gauff hogged the headlines.

"I'm just speechless, I honestly can't believe this. I've dreamed about this moment since I was five years old... I've worked so hard to get here," said Kenin, who was a baby when her family moved to America with just a few hundred dollars to her name.

"She came up with some really great shots. I knew she wasn't going to give it up to me -- I really had to fight out here. There's a reason she's number one."

Kenin's win came on a day when temperatures hit 38 Celsius (100.4 Fahrenheit), prompting play to be suspended on outside courts -- following earlier problems with bushfire smoke, downpours, wind and even muddy rain at the season's opening Major.

The American will face another heavyweight in Saturday's final, with the second semi featuring Wimbledon champion Simona Halep and Garbine Muguruza, the two-time Major-winner who is back in a hot streak of form.