Australia has marched into the semi-finals of the T20 World Cup with a six-wicket win over hosts South Africa, sparked by Tahlia McGrath’s 33-ball 57 and Georgia Wareham’s 2-18.

Ash Gardner, who took her 50th T20I wicket earlier in the night, helped the defending champions round out their group-stage campaign undefeated with her unbeaten 29-ball 28.

Her 56-ball, fourth-wicket 81-run stand with McGrath was the cornerstone of Australia’s successful 125-run chase in the second fixture of Saturday night’s double-header at the St George’s Park Stadium in Gqeberha.

No. 6 Grace Harris hit a match-sealing four first ball as Australia overhauled the target with 21 deliveries to spare.

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“It’s a big relief. I haven’t been batting overly well and was lacking some time in the middle, so I was a bit nervous to start off with,” said player of the match McGrath.

“I seem to thrive in difficult situations and no good in the easier ones. I just love a challenge. I love the fight.

“I keep it pretty simple when it’s a tense situation out there. It seems to be working for me at the moment. So, yeah, I’ll just roll with it.”

Earlier, the absence of Alyssa Healy, ruled out as a precautionary measure with soreness in her left quad, forced a rejigged batting order.

Ellyse Perry, promoted to partner opener Mooney in Healy’s stead, fetched two fours in her eight-ball stay. She was, however, caught by first-slip off Marizanne Kapp to the delight of the 8367 crowd at Kapp’s home ground.

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Left-arm spinner Nonkululeko Mlaba added spectacle by having Meg Lanning bowled behind her legs with a top-of-off-stump strike.

Mooney was next to depart, Kapp’s full-length pinging her toe plumb lbw.

A see-saw first 10 overs saw Australia slump to 3-40 by the seventh and 3-60 by the halfway mark.

Gardner and McGrath rode their luck subsequently, their wild swings sending edges flying beyond patrolled areas.

Neither pacers nor spinners could keep McGrath quiet.

The 27-year-old stroked a flurry of fours either side of the wicket, the second of three in a brace in the 16th over bringing up her fifth T20I fifty off just 29 balls.

A disciplined showing from Australia’s seven-pronged attack, Wareham’s 3-0-18-2 included, had earlier restricted South Africa to 6-124 after Lanning opted to bowl.

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Australia coupled its sterling performance with the ball with enviable fielding, saving at least 15 runs through their boundary-riding alone.

Annabel Sutherland, Healy’s replacement in conditions favouring pace, could have had a wicket as early as her third ball.

But Wareham, stationed at short midwicket, shelled Laura Wolvaardt’s straightforward catch when she was on 13.

The 23-year-old opener could, however, add only another six runs to her tally as Perry got her to nick a length ball behind.

Mooney, shouldering wicketkeeping duties in Healy’s absence, snared it to break the run-a-ball 54-run opening stand.

Wolvaardt’s wicket at the close of the ninth over triggered a top-order collapse: South Africa lost four wickets in 18 balls for just 23 runs.

Darcie Brown elicited a thick edge off first-drop Kapp in the 11th over.

Wareham then played her part with aplomb using the on-the-wane surface where England beat India by 11 runs earlier in the day.

In a double-wicket 12th over, the 23-year-old first grazed the leg stump of Tazmin Brits, the opener falling five short of a 50.

Four balls later, she had Tryon caught off a carbon-copy of the pull she had reprieved Wolvaardt off, at the same position: short midwicket.

Gardner then found her 50th T20I wicket in opposition captain Sune Luus in the last over of the innings.

-AAP