"We've been picked for this squad for a reason, and that reason is to play against England and do all we can to topple them on their home ground," the Montpellier back-rower said.
"This World Cup in England is a once-in-a-lifetime opportunity: we're not going to let it pass us by. Friday night is a massive, massive opportunity for Fiji."
Pool A is widely regarded as the pool of death - with England, Australia, Wales and Fiji vying for the two quarter-final slots - but McKee describes it as the pool of opportunity.
"We're looking to those games to take some scalps and progress to the playoffs. There's going to be a lot of twists and turns in the pool," he said.
"We know it's a massive challenge ahead of us. England are a very strong side, if we let them they can dominate the game. The atmosphere, I think, will be great, it's a big motivator for the players."
McKee said he had a fully fit squad available and would be holding nothing back against England.
"We'll be playing our strongest team," he said, leaving open the option of rotating players when they play Australia five days later.
McKee could not fault his side's buildup, saying the sharp training session on Monday had put them into game mode.
"We really focused on the things that we need to do in the game. It's about the game."
McKee's focus since taking over as Fiji head coach last year has been in making the side more competitive at the set-piece and the improvement was evident when they beat Pacific Islands arch-rival Samoa to win the recent Pacific Nations Cup tournament.
