Fiji issued a warning to RWC group rivals England, Wales and Australia, when they thrashed Canada 48-17 in London on Sunday.
It was the Pacific Islanders' final warm-up match before they face hosts England in the global showpiece's opener at Twickenham on September 18.
Fiji coach John McKee said his team want to be competitive at the World Cup and their aim is to reach the quarter-finals.
"We know what a good side England are and we need to be at our absolute best to topple them, but we have the belief that we can do well," he told AFP.
"It's a big task, but the great thing about sport is that challenges bring out the best in people and I believe that with the team we've got we are going to cause some upsets in this competition.
"We don't see them as upsets, but other people may do. We've got the England game, but this pool isn't all about facing England, it's about all four games.
"There will be a lot of twists and turns. Teams are going to beat each other, win games and lose games, so it could be very tight at the end. We want to get out of the pool phase."
Fiji captain Akapusi Qera echoed his coach's sentiments.
"We're not here to make up the numbers," he said.
"We're here to stamp our mark as well. We'll be ready for England."