Fast bowler Trent Boult led an inspired attack as New Zealand bundled out Sri Lanka for 171 on Thursday as the Kiwis look to earn a semi-final spot at the World Cup.

New Zealand elected to field first and the bowlers backed up the decision with regular wickets despite an attacking 51 by Kusal Perera in Bengaluru where rain is expected in the evening.

Sri Lanka slipped to 128-9 before Maheesh Theekshana hit an unbeaten 38 and frustrated the Kiwi bowlers in a 10th-wicket stand of 43 with Dilshan Madushanka, who made 19, before the innings folded in 46.4 overs.

Left-arm quick Boult returned figures of 3-37, while fellow pace bowler Lockie Ferguson, spinners Mitchell Santner and Rachin Ravindra took two wickets each.

Sri Lanka lost half their side for 70 inside 10 overs after Ferguson sent back the left-handed Perera, who hit nine fours and two sixes in his 28-ball knock.

Perera was dropped on nought by wicketkeeper Tom Latham off Tim Southee who struck with a wicket on the next ball to send back Pathum Nissanka, caught behind for two.

Boult then got the wickets of skipper Kusal Mendis (six), Sadeera Samarawickrama (one) and Charith Asalanka (eight), who was given not out but the Kiwis successfully reviewed the decision in their favour.

The Mendis strike was Boult's 50th World Cup wicket Cup to enter elite company including Glenn McGrath, Muttiah Muralitharan, Mitchell Starc, Lasith Malinga and Wasim Akram.

Mitchell Santner struck twice to get the key wickets of Angelo Mathews (16) and Dhananjaya de Silva (19).

Mathews looked dejected after being caught at slip off Santner's left-arm spin in his first innings after his "timed out" dismissal -- the first in international cricket history -- in the team's previous loss to Bangladesh.

The Black Caps have lost four straight matches but remain slight favourites in the hunt for the remaining semi-final spot as they have a better run rate than rivals Pakistan and Afghanistan.

Sri Lanka, who lie ninth in the 10-team table, are already out of the semi-final race but have Champions Trophy qualification on the line.

The top seven teams from this World Cup will gain entry into the 2025 tournament along with hosts Pakistan.

Brief scores: Sri Lanka 171 all out in 46.4 overs (K. Perera 51, M. Theekshana 38 not out; T. Boult 3-37)