England have a real sense of "optimism and belief" before their opening game World Cup game against Argentina on Saturday, says lock Maro Itoje.

However, Itoje says they want to play "good winning rugby" at the World Cup.

"I genuinely believe that come Argentina on Saturday night, we will take a big step forward," Itoje told BBC Sport.

"There is a real sense of optimism and belief about what we can do and where we can take it."

England lost three out of their four warm-up matches which included a first defeat by Fiji, but Itoje believes the potential in the squad is "huge".

"It is important when you go through those tough periods to stick together and get stronger. We are not in a position where we are suffering from poor quality in terms of staff and players," Itoje added.

"We have high quality in both areas, it is just about us allowing us to put it all together.

"Our potential is huge and I have always thought that. Over the last few games we have not shown what our potential is.

"That has been a great learning curve for us, but if we get this one right then we are on our path and journey with so much to look forward to."

Itoje added that the opening game against Argentina is an "incredibly important" game for the group.

The Pumas won 30-29 against England at Twickenham in November, but since that victory went on a six-game losing run.

A victory for England over the highest ranked side in the pool, would make them heavy favourites to progress to the quarter-finals, as one of the two top-ranked sides in the pool.

"Certain games aren't just another game, certain games due to the magnitude of the game are incredibly important," said Itoje.

"We want to be a team that plays good winning rugby and we want to have a dominant set-piece, our decision-makers need to make good decisions and find space and put us in the right area in the field."

England also face Japan, Chile and Samoa in Pool D and will avoid one of the top five-ranked sides if they make the quarter-finals.