The Rugby World Cup will once again be won by a team from south of the equator as the semifinal line-up was confirmed Sunday with Australia and Argentina joining New Zealand and South Africa in the last four.

Twickenham once again produced a thriller as the Wallabies edged Scotland 35-34, while for the second day running the quarterfinal at Millennium Stadium was a somewhat more one-sided affair as the Pumas beat Ireland 43-20.

The two teams now go head-to-head next Sunday for a spot in the final — though the Scots will be feeling particularly aggrieved they are not still in the mix.

Vern Cotter's team was on the wrong end of two controversial decisions that ended up costing it 10 points and ultimately the game.

The final nail in the coffin came in the final minute when Scotland was harshly ruled offside by referee Craig Joubert and Bernard Foley kicked the penalty to seal the win.

"They go to the TMO for everything else these days, so why not go to the TMO for that?" asked Scotland captain Greig Laidlaw, who had kept his side in the game with five penalties and two conversions.

While the officials were applying the law to the letter — the Television Match Official can only be used in the act of scoring, whether a kick was successful and potential foul play — it wasn't the first time the pair had ruled against the Scots.

Sean Maitland was shown a yellow card early in the second half after Joubert consulted with Ben Skeen and determined the Scotland wing had deliberately knocked on, much to the astonishment of most in the crowd of 77,110.

A minute after the decision, Drew Mitchell crossed for the second of his two tries, with Foley, who will join Ricoh Black Rams after the tournament, adding the extras as the Aussies regained the lead after trailing 16-15 at the break.

"Most of these questions are about the referee," said Cotter as the post-match press conference was dominated by questions about the officials' decisions.

"I am not in the referee's position. I think if Sean had caught that ball he would have probably scored. It was a 50-50."

Earlier in Cardiff, Argentina stunned Ireland with two early tries and although the Irish fought back to 23-20 early in the second half, it was the Pumas who finished stronger to ensure the Irish once again failed to progress from the last eight — their record now being six quarterfinal appearances and six losses.

"Yes, obviously we're very disappointed to lose in such a big game," said Ireland captain Jamie Heaslip. "We didn't help ourselves at the start. We got back in the game, got it back to three points, but couldn't take our opportunities."

Juan Imhoff grabbed a brace of tries for Argentina and said the team would celebrate briefly before starting preparations for the semifinal next Sunday.

"It was a very tough game," said Imhoff. "We worked hard to get this victory. Now we want to enjoy the moment but we know we've got another hard game to come."

At Twickenham, the Scots came into the game knowing they were carrying the hopes of the Northern Hemisphere.

And they carried the responsibility on broad shoulders.

They may have been outscored five tries to three, but they never gave up despite things going against them.

The Wallabies were at times breathless as Adam Ashley-Cooper, Mitchell and Michael Hooper all crossed in the first half.

But their defense was also exposed with Peter Horne going over for the easiest of tries in the first half.

The second stanza saw Mitchell and Tevita Kuridrani cross the whitewash for the Wallabies with Foley finally getting his radar working after missing three shots in the first half.

But the Scots kept hitting back with Tommy Seymour touching down and Laidlaw knocking over kick after kick.

Scotland may have been playing at the home of the "auld enemy," but the neutrals in the crowd was very much behind the men from north of the border and an intercept try from Mark Bennett seven minutes from time lifted the roof off the stadium as the tartan-clad fans and their new-found friends sensed a famous win.

But then came Joubert's decision. Foley kept his nerve despite the boos and Australia moved on while the Scots packed up for home.

"All credit to Scotland. They made a great game of it," said Australia coach Michael Cheika. "We had to get through it somehow. We were a little bit flat in the first half. We were not at our best today but we got the job done. We got five tries and we move on."

World Rugby's motto is "World in Union," but after Sunday's results it is more a case of a hemisphere in union.

"It does mean everyone knows each other very well," said Cheika.