Italy pulled off a vital bonus-point 27-10 victory over the United States on Tuesday to set up a showdown with Ireland in their final Rugby World Cup pool match.
The win put Italy on 10 points, three behind Ireland, with their winner-take-all match on Sunday to decide the second Pool C quarter-finalist with Australia, who still have to play Russia, virtually assured of going through.
Playing with a strong breeze behind them, Italy scored three tries in the first half but then had to struggle for 26 minutes in the second before the crucial fourth and final try came.
In the face of dogged defence by the US, Italy were unable to cross the line and the breakthrough came by way of a penalty try after the US pack eventually collapsed in the face of a relentless onslaught.
"It was a tense build-up to this game because I respect what USA have done in this tournament," said Italy coach Nick Mallet.
"But our major advantage is our scrum and we dominated them completely. I'm sorry for the spectators, it might not have been as open as they would have liked, but you play to your strengths."
Italy's most potent weapon was the forward pack led by seasoned Martin Castrogiovanni, who put in a man-of-the-match performance in a front row that ground the US into submission.
But although Italy dominated the United States up front, until the penalty try came there had been no reward for their frequent rejection of penalties in the second half in favour of scrums.
"You can tell they're a Six Nations team and they've gotten some wins because the know what to do under pressure," said US captain Todd Clever.
"We've given what we had but in the end it wasn't enough against a strong side tonight."
It was evident Italy meant business from the kick-off and they were on the board within two minutes when captain Sergio Parisse scored after Mirco Bergamasco and Leonardo Ghiraldini exposed the US defence on the right flank.
Tomasso Benvenuti, who scored twice against Russia last week, was within a whisker of scoring soon after but knocked on trying to gather the ball on the line.
It was the first of three occasions when the television match official was called in to adjudicate as Italy spent long periods camped on the United States line.
Having weathered Italy's opening storm, the United States had their best period on attack in the second 10 minutes when fought their way deep into Italian territory.
From a lineout, centre Paul Emerick broke through two limp tackles to send fullback Chris Wyles across for the try.
Wyles converted and exchanged penalties with Bergamasco to have the score tied at 10-all after 30 minutes when Italy regained control and scored twice in the closing stages of the half.
Fly-half Luciano Orquera sliced through a gap around the ruck to score their second try and prop Martin Castrogiovanni burst his way over for the third and to put Italy ahead 20-10 at the turn.
The second half was a turgid affair as Italy's quest for the vital fourth try dominated proceedings.
Parisse and Orquera were both brought down just short of the whitewash before Italy eventually achieved their target with the penalty try.