Australia will play New Zealand in their first junior rugby world championship final after defeating England 28-16 at Estadio El Coloso del Parque in Rosario, Argentina on Friday Australian time.

The Australian under 20s were dangerous with ball in hand and scored two first-half tries through winger Aidan Toua and fullback Luke Morahan before Sevens star Kimami Sitauti put the result beyond doubt with a brilliant try five minutes from time to eliminate England, who have finished runner-up to New Zealand in the past two tournaments.

Brumbies flyhalf Matt To'omua again proved ever-reliable with the boot, kicking three penalties and two conversions from seven shots at goal.

Traditional trans-Tasman rivals New Zealand await Australia in the final on June 21 after the Kiwis made light work of South Africa 36-7 in the other semi-final.

Captain Jake Schatz says he is delighted Australia will compete in their first championship decider.

"We had no preference to who we play in the final. Whoever it is we'll take plenty of confidence into that game and we want to win it, we want to take out the title," Schatz said.

"Again, I'm very proud of the front row and the tight five in the scrum, they got us on the front foot in that department but the lineout, we still need to work on ahead of the final which is really important to us, we'll continue to try and fix that up."

Australia drew first blood through a To'omua penalty but winger Sam Smith hit back with a try out wide to give England an early 5-3 advantage, which proved to be the only time coach David Nucifora's side would trail on the scoreboard.

Elusive winger Toua restored Australia's lead after finishing off a clever piece of play from centre Robbie Coleman before Morahan showed his class and cut back on a perfect angle to score untouched under the posts to give his side a 17-8 lead after To'omua's conversion.

Following a second successful penalty to To'omua, a dominant Australia went into the break with a healthy 20-8 advantage.

The Schatz-skippered side wouldn't have it all their own way with England fighting back in the second-half, as hard-hitting defence and dominance at the line-out appeared to unsettle the free-running Australians.

The sides traded penalties and England still needed to score twice to run down the 12-point margin with 13 minutes remaining before blitzing centre Sitauti beat four defenders with a flash of individual brilliance to put Australia through to their first IRB junior decider and assure his side of their best-ever result at the tournament after they finished fourth last year and fifth the year prior.

England replacement Jonny May powered over for a consolation try in the final minute to narrow his side's three-tries-to-two defeat.

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