Mental rather than physical strength is a key ingredient if Auckland City FC are to carry out the unthinkable and topple South America's best side in the club World Cup semi-finals.

Coach Ramon Tribulietx admits a continuation of their giant-killing run in Morocco is dream material in Wednesday's semi-final against San Lorenzo of Argentina.

He says the degree of difficulty has risen sharply following their upsets of Moroccan hosts Moghrab Tetouan on penalties and ES Setif of Algeria 1-0.

Repeating the dose begins before kick-off in Marrakesh, says Tribulietx, who has been a psychologist as much as a coach for his semi-professional players this week.

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"It's about preparing ourselves not only on the field but also mentally convincing ourselves that we can actually compete against these guys," he said.

"The game is a massive step up, with all respect to the African champions.

"We're talking about the champions of Argentina - a real football team - with a lot of history behind it."

Tribulietx accepts physical recovery ahead of a third tough game in a week will also be crucial.

They can help themselves physically if they can continue to hold a fair percentage of possession, which has been a surprising element of their two wins.

A 3-0 loss to Mexican club Atlante in the quarter-finals of the 2009 tournament in Abu Dhabi is still on the mind of Tribulietx, who remembers his team chasing the ball all game.

"That was the last Latin side we played against and it was a very good football side with a clear idea on keeping the ball," he said.

"As we all know, we've got a different flair now. We try to keep the ball when we've got the opportunity."

Captain Ivan Vicelich, 38, says his team's achievement matches anything he has achieved in a long career featuring stints in Europe and Japan, along with a New Zealand record 88 caps.

Even the All Whites' unbeaten pool performance at the 2010 World Cup in South Africa doesn't top it.

"It sits besides anything I've achieved in my career before," he said.

"We have to enjoy this achievement because we've now got a once in a lifetime opportunity in front of us."

Whatever the outcome it will be lucrative.

A loss in Saturday's third-fourth play-off would still net Auckland City $US2 million ($A2.15 million) while the winners get $US2.5m.

The finalists will win $US5m and $US4m.

Prize money will be split evenly four ways - to the Auckland City club, its players, New Zealand Football and the other national domestic teams.