O'Neill said: "Through experience, the players have matured. I think there's a good belief in the camp that maybe didn't exist a couple of seasons ago.

"It's an inner self-belief. It's not one that is flaunted, it's an inner self-belief that we can come out and compete.

"We know what we have to do, we know we must compete for almost everything at every given minute and while every single international side has limitations somewhat, we are going to try to stay as strong as we possibly can and play to our strengths, which is the most important thing.

"It's something we do, use that experience we've had in the last couple of years to some good effect, and that's what we're going to try to do."

O'Neill and his players arrived in Denmark under no illusions about the size of the task ahead of them as the Danes are ranked 19th by FIFA, seven places above the Republic.

However, the two-legged victory over Bosnia-Herzegovina which booked their place at the Euro 2016 finals remains fresh in the memory.

Midfielder Robbie Brady is hoping they can draw on the experience of a priceless 1-1 draw in Zenica - as well as famous victories over Germany, Italy and Wales - over the next few days.

Brady said: "Over the last couple of years, we've shown in big games what we're capable of producing. The lads who were there a couple of years ago can use anything from that night.

"To go in with the belief when you're that close to a World Cup, it's there for the taking for both sides. If we can take anything from that game, it will be belief."

Denmark boss Age Hareide knows exactly what to expect from the Republic and the spirit they will have to break to get past them, although Brady insists that will be easier said than done.

He said: "They can try, but we'll see. We're ready. We've done our homework and we're prepared, so we'll have to wait and see."