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Australia faces the more-fancied South Americans in an inter-continental play-off at the Ahmad bin Ali Stadium in Qatar on Monday (Tuesday 4am AEST).
The winner earns a spot at November's finals.
For the loser, it's a trip home.
Arnold firmly believes his team is primed to take Australia to a fifth-straight World Cup despite the odds being stacked against them.
"You've got to be ready for anything that Peru, individually, throw at us," Arnold said.
"I just really believe in our players.
"It's a one-off game and it's a final.
"That's crystal clear to everybody. That is fine.
"I think the Peruvians will be surprised by the improvement of the Australian footballers technically."
Arnold may yet make a couple of changes to his line-up from the team that beat the United Arab Emirates in an Asian play-off last week.
Defender Trent Sainsbury missed that match with a knee injury but is pushing for a return and could start at the expense of youngster Kye Rowles.
Right-back Nathaniel Atkinson is also fighting to retain his spot after being troubled by Emirati winger Harib Abdalla in the 2-1 win with Fran Karacic a possible replacement.
A-League Men golden boot Jamie Maclaren could also start up front with Mathew Leckie moving to wing at the expense of Adelaide United's Craig Goodwin.
Jason Davidson (hamstring) will definitely miss the match while striker Adam Taggart is unlikely to feature after struggling to overcome a thigh complaint.
"We've looked at Peru a number of times, we know exactly what they're about," Arnold said.
"It's more about what we do. Getting on the pitch and making sure we do our job to win the game.
"We have respect for Peru but we believe also in ourselves."
While Australia's 500 or so supporters will be dwarfed by the approximately 12,000 Peru fans in the stands, there'll be one special guest in the crowd for the team in Harry Souttar.
The Scottish-born defender, whose qualifying campaign came to an end when he damaged an ACL during the goalless draw with Saudi Arabia in Sydney last November, will be travelling from England to watch and see if his teammates can reach the World Cup.