With his future secured, the 22-year-old set his sights on hitting the ground running when he and his team-mates return for pre-season training on July 11.

Leadbitter said: "I'm pleased to sign. I'm happy at the club and I want to help drive it forward next season - I want to kick on.

"To me, every pre-season is tough, I'm sure this will be no different.

"We will have to work hard. I personally can't wait for next season.

"I've been doing some fitness work, getting ready for two weeks' time - you've got to in football now."

Leadbitter was entering the final season of his previous contract and should break through the 100-appearance barrier next term, having already played 93 games for Sunderland and scoring 19 goals.

He also earned his first England Under-21 caps last season.

Leadbitter said: "As a Sunderland fan, I want the club to be stronger.

"I think I came on as a player last season and I want to improve again. I always expect better of myself - I want to learn and play as much as possible.

"The Premier League is a tough league - possibly the best in the world - and it'll be another big challenge for us next season.

"Hopefully we can improve and become a solid Premier League outfit.

"This is my club and I enjoy playing here. We have a good set of lads and hopefully there will be one or two new signings to make the squad better."