MIAMI, United States (AFP) — Venus Williams rolled back the years to send world number one Angelique Kerber crashing out of the Miami Open on Wednesday and advance to a semi-final showdown with Britain’s Johanna Konta.

Williams, at 36 the oldest woman in the field, downed Kerber in straight sets, winning 7-5, 6-3 while Konta fought back to beat Romania’s Simon Halep 3-6, 7-6(9/7), 6-2.

Both results had the element of surprise about them with Kerber the top seed and Halep the third and in good form, but they set up what should be a fascinating contest on Thursday.

The other semi-final pits Denmark’s Caroline Wozniacki against second-seed Karolina Pliskova of the Czech Republic.

With the local crowd behind her, Williams, a three-time winner at Miami clearly believed she could topple the German but the first set saw both players struggle to hold their serves.

The American broke Kerber four times while Williams failed to hold serve twice, but the contest was more one-sided in the second set.

Williams raced to a 4-1 lead before Kerber broke back and started to produce some great shots as she battled in vain to save the match.

The victory over Halep means Konta becomes the first British woman to reach the last four at Miami.

“I’m really happy that I’ve come through and I am just looking forward to my next round – it’s going to be a tough one,” said Konta.

Halep settled well in the opening set, with her powerful forehand dominant, but Konta fought back well in the second.

The Australia-born Konta broke early to establish a 3-0 lead but the gritty Romanian clawed her way back winning the next three games while her opponent failed to make the most of her openings in what was an error-strewn contest.

Nonethless, Konta stuck at her task and was able to break again when Halep was serving for the match and force a tie-break which she eventually won 9-7 to take the pair into the third game.

There was a tense discussion between Halep and her Australian coach Darren Cahill.

Konta broke in the fifth game of the deciding set and visibly growing in confidence she broke again to take a 5-2 lead and serve out for the match.