CARDIFF, Wales -- Argentina delivered another jolt to European rugby by dismantling Six Nations champion Ireland with some backline brilliance to win 43-20 and reach the Rugby World Cup semifinals on Sunday.

Long-renowned for their strength in the forwards, the Pumas provided another illustration of their improvement out wide by scoring four tries -- two in the opening 10 minutes to help open up a 17-0 lead, and two more in the final 11 minutes when the Irish were taking risks.

Juan Imhoff -- a gliding winger and a star of the tournament -- crossed either side of halftime, while centre Matias Moroni and fullback Joaquin Tuculet scored the other tries for Argentina, which advanced to the semifinals for only the second time.

The Irish are yet to reach that stage, despite their rich rugby history. They will rue their slow start and the absence of key elements of their leadership group in captain Paul O'Connell, star flyhalf Johnny Sexton, and flankers Sean O'Brien and Peter O'Mahony, who were either injured or suspended

"As difficult as it is to be going out of the World Cup, it was a fantastic Argentina performance and a performance our players will learn from," Ireland coach Joe Schmidt said. "There's a lot of my players who have never, ever been in a match of that intensity."

Four seasons playing the southern hemisphere behemoths in the Rugby Championship have proved invaluable for the Pumas, raising their standards and making the team produce a better all-round game. There will be a new Argentine franchise -- made up solely of Pumas internationals -- playing in Super Rugby from 2016, which can only improve the national team.

"Since 2012, the growth of our rugby has been enormous," Argentina coach Daniel Hourcade said. "We started building, we started changing. Playing the best on a yearly basis requires a level of preparation and you get used to it. The players love it."

It's the third time that Ireland has been eliminated from a World Cup by Argentina -- after 1999 and 2007 -- and another blow for the northern hemisphere following losses for Wales and France on Saturday.

Nicolas Sanchez was Argentina's heartbeat -- "imperious," according to Schmidt -- interchanging with centre Juan Martin Hernandez at first receiver and playing flat to cause the Irish defence problems. He kicked 23 points and missed just one of his 10 shots at goal, making Ireland pay for their indiscipline, particularly at the breakdown.

From a Sanchez bomb in the third minute, Tuculet leapt highest and set up a phase that ended with winger Santiago Cordero putting in Moroni for a try in the right corner.

The second try came down the right, too, as Cordero ran into space and kicked on. Imhoff was the quickest of three Argentine chasers and managed to collect and ground before the dead-ball line.

When Sanchez booted a 14th-minute penalty for 17-0, the Irish needed to produce the greatest comeback in Rugby World Cup history.

"Building that scoreboard pressure allowed them some confidence and dented the confidence of our group," Schmidt said. "A team that was probably lacking a bit of experience, a few cool heads to manage the various areas of the field."

A yellow card three minutes later to Argentina prop Ramiro Herrera for an illegal tackle gave Ireland hope, particularly when Robbie Henshaw's pick-up-and-pass set free Luke Fitzgerald, on as an injury replacement for Tommy Bowe, to cut inside on the left wing and score a try converted for 20-10 at halftime.

Driven on by vociferous support under a closed roof, Ireland began to challenge better at the breakdown and frustrate Argentina. And early in the second half, Fitzgerald provided more cutting edge by making a break through the middle and delivering a perfect offload that Jordi Murphy charged onto and over the line.

Sanchez and Ian Madigan booted penalties, and Ireland was only 23-20 behind with 20 minutes left.

But many of Argentina's top names have had two weeks of preparation for this match, after being rested for the final pool game, and their superior fitness told near the end. Tuculet and Imhoff burst through a tiring defence for converted tries that sent the Irish home early again.