Ashleigh Barty saluted one of the grass-court greats after she beat Venus Williams to reach the Birmingham Classic semi-finals.

The Australian will become the new world number one this weekend if she carries off the title, and a 6-4 6-3 victory against five-time Wimbledon champion Williams kept her right on track.

Barty, 23, arrived in England as the newly crowned French Open champion and made sure 39-year-old Williams would not halt her winning run, which now stands at 10 matches.

She called Williams "an absolute champion" and said playing the American had given her "a really special memory".

"There's only one Venus so I think you have to make the most of the opportunity," Barty said, in an on-court interview.

"I knew my level would have to be very good today to make it a contest and I'm glad that I was able to do that."

As for whether Barty will still be playing at Williams' age, the Queenslander was quick to say: "Absolutely not. I can guarantee I will not be here at 39, I'm sorry."

Asked about the prospect of reaching number one with this weekend's title, Barty said: "I'm not there yet, am I? Any time you can get yourself deep into a tournament, it's exciting.

"There's no doubt you start thinking ahead, it's natural that it happens, but it's important for me to come out and focus [on Saturday], try and do the best I can, and if I happen to play another good match and get another win, it's another opportunity."

Barbora Strycova, who has floated the idea she could partner Andy Murray in mixed doubles at Wimbledon, showed her singles prowess in beating fellow Czech Kristyna Pliskova 6-2 6-4 to set up a last-four clash with Barty.

Latvia's Jelena Ostapenko looked to be sailing through to the semi-finals when she led Croatian Petra Martic by a set and 4-0 but let the match slip away, serving 20 double faults on her way to a 6-7 (4-7) 7-5 6-1 defeat.

Martic will face Germany's Julia Goerges who beat Kazakhstan's Yulia Putintseva 6-3 6-2 in the final singles match of the day.