LONDON -- Adam Ashley-Cooper's third try set up by a brilliant run from Drew Mitchell secured Australia's 29-15 win over Argentina and its spot in the Rugby World Cup final against archrival New Zealand on Sunday.

It was the deciding match that trans-Tasman organizers of the first World Cup had in mind in 1987, but didn't eventuate for eight editions.

Australia and New Zealand have each won the World Cup twice -- the All Blacks in '87 and last time around in 2011, each time on home soil, and the Wallabies won in 1991 and '99, both previous times the tournament has been staged in Britain.

The much-anticipated exhibition of running rugby between the reinvigorated Wallabies and the Pumas lasted a half hour or so before both teams settled primarily into a percentages game, kicking for territory and sweating on errors triggered from brutal defence. The Australians crossed for tries in the second, 10th, and 32nd minutes and Argentina stayed in touch with three penalty goals from the ever-reliable boot of Nicolas Sanchez.

But there wasn't a try scored for another 40 minutes until Ashley-Cooper crossed for his third -- moving him to joint fifth on the all-time World Cup list with 11 -- in the 72nd to release the pressure on the Wallabies.

It was another veteran winger who deserved credit for the one that sealed it, as Mitchell burst down the left sideline before stepping inside and crabbing his way across field beating five defenders before releasing to the right, where Ashley-Cooper picked it up on the bounce and strolled over untouched.

"We left the game a bit open, which really suited them," Wallabies coach Michael Cheika said. "Then we settled into some structure, which suited us. Defence did well -- we didn't let them in for a try.

"Overall, we scored four tries -- we can improve again."

The Australians led 19-9 at halftime but were still under pressure at the scrum, as expected, and from Sanchez.

Foley missed a goal just after the break, and the Pumas twice reduced the margin to seven points as the kickers traded goals.

The Pumas tried early to play with the same endeavour and panache that earned them a 43-20 win over Six Nations champion Ireland in the quarterfinals last week, but it backfired to start with.

Running the ball from deep cost them dearly, when lock Rob Simmons intercepted Sanchez to score near the posts after 68 seconds, the fastest try in World Cup history. The Pumas persisted with the attacking strategy, but simple turnovers cost them repeatedly as David Pocock and Michael Hooper poached turnover ball.

Stung after last week's last-minute 35-34 win over Scotland, the Wallabies were more controlled but still expansive in attack when they could be, leading to 113-test winger Ashley-Cooper's diving tries into the left and right corners -- both from sprinting onto long, floating cut-out passes from flyhalf Bernard Foley and centre Matt Giteau.

Argentina had some serious setbacks in the first half. Flying winger Juan Imhoff staggered off the field after a head knock, lock Tomas Lavanini was sin-binned for a no-arms shoulder charge on Israel Folau, and skipper Agustin Creevy succumbing to a leg injury that threatened to keep him out of the semifinal.

The Argentines stayed in touch via the reliable and accurate boot of Sanchez, and narrowly missed a try that could have swung momentum in first-half injury time, when the flyhalf made a line break, wrong-footed Mitchell and unloaded to Hernandez. But the back-of-the-hand flick pass from Hernandez went to ground in the right corner.

The Pumas reverted to the tighter play they're famous for, with judicious kicking, and banking points from the powerful scrum earning penalties.

Still, even with Diego Maradona in the 80,025-strong crowd, which heavily backed the Pumas with football-style chants of "Ole, ole, ole, ole, Pu-mas, Pu-mas," Argentina was unable to break through to reach its first Rugby World Cup final. The Pumas will play South Africa in the third-place match, with a chance to equal their finish in the 2007.