Blues Winger Tevita Li scored two tries as New Zealand outplayed Ireland 25-3 to book a semi-final place at the Under 20 World Championship in Italy.

New Zealand will play France in Calvisano on Monday while South Africa and defending champions England will square off in the other semi-final in a repeat of last year's final.

The New Zealanders led the previously-unbeaten Irish 11-3 after a tense first half at Viadana but blew the game open with two tries soon after the break before a scoreless final half-hour. Blues wing Li bagged his first try in the 17th minute after Ireland had dominated a scrappy opening. He danced over under the crossbar three minutes after the break before another Blues player, flanker Blake Gibson, powered across from close range.

First five-eighth Otere Black kicked 10 points while opposite Joey Carbery landed an early penalty for an Irish side who were abrasive up front but lacked the necessary backline panache.

France are also unbeaten, topping their pool courtesy of a 30-18 upset of England. The English qualified for the semi-finals as the best second-placed team from the three pools.

Australia's hopes were dashed by a 46-13 loss to South Africa in the other clash of two unbeaten teams. The Australians trailed from the outset and never recovered, leaving them to fight it out with Ireland, Wales and Scotland for places fifth through eighth.

New Zealand are the only team to have qualified for the semi-finals at all eight editions of the annual junior championship. They won the first four tournaments but South Africa and England (twice) have claimed the silverware since 2011.