Fourie du Preez has stressed that the pressure is still on South Africa ahead of their final Rugby World Cup Pool B match against the United States at the Olympic Stadium on Wednesday.

The Springboks suffered a humiliating loss to surprise package Japan in the opening game of the tournament in Brighton, but have responded impressively to what was the biggest shock in World Cup history.

A crushing 46-6 defeat of Samoa was followed by a 34-16 victory over Scotland at St James' Park on Saturday, a result which put Heyneke Meyer's side top of the pool.

Another triumph over the United States in London would ensure the Springboks advance to the quarter-finals as Pool B winners to set up a showdown with Wales or Australia.

South Africa will be expected to have too much quality for a USA side that are already out of the tournament after losing both games so far, but new captain Du Preez is not getting ahead of himself.

He said: "After the match against Japan, we were under immense pressure, the worst I've ever experienced, and although the character of the team came through, we're still under the same pressure.

"We knew we had to beat Samoa and Scotland. Now we're facing the USA and if we don't win, we're on the plane home and out of the tournament.

"But we know what will work for us on the field and tomorrow (Wednesday) we simply have to take that up a notch. There is still a lot of desperation and hope, but our only focus for now is on the encounter against the USA."

Meyer has made only two changes to his starting line-up, with Lwazi Mvovo replacing the injured JP Pietersen and Bryan Habana switching to the right wing.

Frans Malherbe is preferred to Jannie du Plessis at tighthead prop. Du Plessis and Victor Matfield will not feature as they recover from knocks. 

Flanker Schalk Burger will make his 17th World Cup appearance, equalling John Smit's South Africa record, while uncapped scrum-half Rudy Paige has been named among the replacements.

Mike Tolkin has made 12 changes to the USA team which was beaten 39-16 by Scotland last time out, with Samu Manoa named as captain for the first time.

Niku Kruger will feature against his country of birth and it will be a special occasion for the scrum-half. 

"Obviously for me it's going to be an opportunity that I've dreamt of for a very long time. It's probably going to be pretty emotional at the same time." he said.

"It's an opportunity to play against some guys that you know have made it big in the sport. It's an opportunity to just go out there and enjoy myself."