World Cup 2015: Kane Williamson, Trent Boult Delighted to be Last-Men Standing

New Zealand's last pair of Kane Williamson and Trent Boult said their edge-of-the-seat, one-wicket World Cup triumph over Australia on Saturday will live in the memory for a long time.

Chasing a modest 152-run target, New Zealand were facing an improbable defeat at 146-9 with number 11 batsman Boult walking in to face the last two deliveries from a rampaging Mitchell Starc who had nearly turned the tables with a career best 6-28. (Scorecard | Highlights)

But Boult survived both balls leaving it to Williamson to hit Pat Cummins for a straight six to bring up the win as a packed 40,000 Eden Park crowd gave them a standing ovation.

The win ensured New Zealand's spot in the quarter-finals with four wins in as many Pool A games.

"I was looking to hit a boundary, ideally a six after the new batsman came in. It was tough so my plan was to hit it and I did," said Williamson, who made 45 not out as New Zealand sealed victory after 23.1 overs.

Boult, who had earlier taken a career best 5-27 which sent Australia crashing to 151, said he was desperate not to let his side down.

"I was pretty pumped up but Kane quickly slowed it down for me, simplified it for me that if I play the two balls then we could move forward." (Boult Proud of His Five Wickets)

New Zealand were cruising along with Williamson and Corey Anderson (26) involved in a 52-run stand for the fifth wicket before Starc pushed them back as five wickets fell for just 15 runs.

"I was just trying to keep that total out of my mind, I suppose, and just bat long enough to have a chance of getting across the line," said Williamson. (McCullum in Awe of Boult and Starc)

"I think Australia bowled outstandingly and made it difficult for us. Starc was superb and swung the ball throughout but it was nice to cross the line, it doesn't matter how you do it. We had a scare but it's nice to win."

Williamson said he didn't realise the damage Starc would cause when he took a single in the 23rd over and the Australian dismissed Adam Milne and Tim Southee.

"Every run looked quite significant and with three wickets left I thought it was okay to get a single but obviously it became tough," he said. (Bring on the Beer, Says McCullum)

"But Trent showed a cool nerve and kept out those two balls and gave me an opportunity, so it was a team effort."

Boult said he just tried to bowl in the right areas when he ripped through the Australians.

"I am just trying to do what I have been doing for the last five or six months. I swung the ball and had some luck with some drag-ons, but definitely I will remember it as it set up a reasonably low total and we chased that down."

Williamson said the win over Australia means a lot to New Zealand.

"Australia are the number one in the world. Whenever you play them it's tough, they don't give you easy runs and wickets so it's tough to play them and winning against them is good."