New Zealand wrapped up their one-day series against Sri Lanka with a game to spare Sunday when Kane Williamson and Ross Taylor orchestrated a 120-run win in game six.

Williamson (97) and Taylor (96) provided the backbone of New Zealand's 315-8 in their 50 overs and Sri Lanka were all out for 195 in the 41st over.

The win puts New Zealand 4-1 up in the seven-match series with one game washed out, and captain Brendon McCullum declared himself satisfied with their World Cup build up.

"It was a pretty clinical performance with the bat and I thought the bowlers certainly did a very good job. Overall another step forward for us and we're very pleased with the series win," he said.

"We've got a couple of different plays. One is to be reasonably aggressive at the start, and if that doesn't come off we know we've still got quality batsmen able to bat a lot of time and still score at a decent runs per over."

But Sri Lanka, still without their injured strike weapon Lasith Malinga, have concerns about the quality of their attack.

"Our concern is with the bowling," stand-in captain Lahiru Thirimanne said.

"We bowled 30-35 overs very good but the last 15 overs we couldn't get the wickets and we also leaked runs. That was disappointing."

There were also problems with their batting with only Kumar Sangakkara appearing at ease in the run chase with 81 off 66 deliveries.

None of the other recognised batsmen were able to get past 30 as New Zealand all-rounder Corey Anderson stamped his mark on the game.

Anderson smacked 40 from 28 balls to support Williamson and Taylor during New Zealand's innings and then took four for 52 with the ball as the Sri Lankan batsmen again showed a lack of fight.

After reaching 146-3, Sri Lanka lost their last seven wickets in 11.4 overs for just 49 runs following a familiar pattern of collapses in the series.

Sangakkara went to the wicket in the 13th over after Tillakaratne Dilshan, who has two centuries so far in the series, was caught behind off Anderson for 21.

Thirimanne lasted for 29 runs and Dimuth Karunaratne contributed 26.

No other batsman reached double figures with the veteran Mahela Jayawardene surviving two reviews before being unquestionably caught for nine.

McCullum, who won the toss for only the second time in the series, opted to bat first after the home side compiled 360-5 on the same wicket on Friday when they won game five by 108 runs.

But it was a disastrous start for the aggressive batsman who was out on the second ball he faced, and fellow opener Martin Guptill struggled to 28 before his departure reduced New Zealand to 59-2.

Williamson and Taylor then mounted their match-winning 117-run partnership for the third wicket.

Williamson, who should have been removed on 27 when Dilshan dropped a regulation chance at short cover, faced 95 balls for his 97.

In his past 14 innings, he has now posted two hundreds and eight half centuries.

Taylor, who has 11 ODI centuries to his name, faced 102 deliveries for his 96.