The victory over the third-seeded Halep means Konta becomes the first British woman to reach the last four at Miami and she will face the winner of Wednesday's other quarter-final between Venus Williams and German world number one Angelique Kerber.

"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.