Opener Finn Allen struck a stunning unbeaten 100 off just 33 balls to lead New Zealand into the T20 World Cup summit clash as they thrashed South Africa by nine wickets in the first semifinal here on Wednesday.Allen struck 10 fours and eight sixes in his innings while his opening partner Tim Seifert made 58 as New Zealand toyed with South Africa bowlers to chase down the 170-run target with 43 balls to spare.Kagiso Rabada (1/28) was the only wicket taker for South Africa.Earlier, Marco Jansen struck a stunning 55 not out in a rearguard action to help South Africa reach 169 for 8 after being asked to bat.Jansen struck two fours and five sixes in his 30-ball unbeaten knock to resurrect South Africa innings after they were reduced to 77 from 5 in the 11th over.Dewald Brevis chipped in 34 while Tristan Stubbs contributed 29.Rachin Ravindra, Cole McConchie and Matt Henry took two wickets apiece for New Zealand.Brief Scores:South Africa: 169 for 8 in 20 overs (Marco Jansen 55 not out, Dewald Brevis 34; Rachin Ravindra 2/29, Cole McConchie 2/9, Matt Henry 2/34).New Zealand: 173 for 1 in 12.5 overs (Finn Allen 100 not out, Tim Seifert 58).