Ashleigh Barty

Ashleigh Barty, Petra Kvitova & Iga Swiatek through to third round

The Australian needed three match points before winning 6-1 7-5 on Arthur Ashe Stadium to pick up her 50th Grand Slam match victory.

The top seed raced through the first set but was unable to convert a match point at 5-3 in the second.

She was broken but responded to eventually serve out the match.

Barty will face American Shelby Rogers or Romanian Sorana Cirstea in the third round.

Barty stuns Venus in Cincinnati

Barty has enjoyed a breakthrough year in 2017, claiming her first WTA Tour title and climbing into the world's top 50 for the first time.

However, prior to Wednesday, the Australian had lost all six of the matches she had played against top-10 opponents.

That winless streak was broken in Cincinnati as Barty overcame a second-set wobble to beat Williams 6-3 2-6 6-2.

"To play Venus on such a big stage is a privilege for me and to play as well as I did, I'm really excited," said Barty.