With France the firm favourites to progress as group winners, Saturday's match could be decisive for Peru and Denmark in the battle for second place.
Under Norwegian coach Hareide, Denmark have become more direct, preferring to move the ball up the field quickly rather than passing it out from the back as they did under former coach Morten Olsen.
They were at their attacking best in the 5-1 playoff demolition of Ireland that secured Denmark's berth at the World Cup and Hareide promised a similar approach against Peru.
"Peru and Denmark is an all important match. France is certainly the favourite," Hareide told reporters.
"If we want to occupy the second place then points tomorrow is very important. We are going to have to go all out tomorrow to see if we can win the match."
Hareide lauded Peru for the speed at which they press forward in attack but is confident in his centre back pairing of Simon Kjaer and Andreas Christensen and his side will try to capitalise on their height advantage.
"We need variation in our game. We need to be able to use our physical strength whenever necessary and win set-pieces," the 64-year-old said.
"We need to get a number of set-pieces to get to the last third of the pitch as quickly as possible. We do have a strength there physically particularly when the ball comes in the air. We need to benefit from that."
The Danes have gone through a rapid transformation following the departure of Olsen, who remained true to the nation's ideal of slick passing football in his decade-and-a-half at the helm that ended in 2015.
Hareide wasted no time in instilling a more pragmatic approach but he acknowledged that the Peruvians have also altered their attacking style of football.
"The biggest change is that they are standing deeper than they did before," he said. "They are not as aggressive."
(Reporting by Sudipto Ganguly; editing by Ed Osmond)
