England's population of around 55 million is 165 times more than Iceland's of 332,000, but Rooney said that ultimately both teams would field 11 players each in Nice.
"We respect Iceland in what they've done in this tournament," Rooney told reporters. "I think the size of the country is a number. They put the same amount of players on the pitch as we do, so it's a fair game in that respect and we hope we can go out and win."
"Fair credit to Iceland, they are a difficult team to break down and we have to be at our best to win -- we know that -- and take our chances when they come," he added.
England manager Roy Hodgson said Iceland's coaching team of Lars Lagerback and Heimir Hallgrimsson and associate Roland Andersson should take much of the credit for their side's unlikely progress to the last 16.
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He praised "the experience and wisdom of Lagerback and Anderson, their ability to organise a team, and their ability to take a group of players and absolutely get the maximum out of them, to make them unbelievably difficult to beat."
They had also introduced a work ethic "which is not seen every day," Hodgson said.
"I think also the character of the Icelandic people and their determination and their ability to survive through hardships -- I'm certain that has been a major factor in their progress as well," he said.
"So, we have to accept the title of favourites and they can go into the game as underdogs. But we know perfectly well it's going to be a very, very difficult game for us and they are going to be a hard team to beat."
(Writing by Brian Homewood. Editing by Adrian Warner.)
