Superman Returns sees the superhero back on the big screen Clips from the movie

"If we want the numbers to come out better than last year's performance, we need to be kicked into high gear," said film tracker boss Paul Dergarabedian.

Up to 40% of box office takings in the US are taken during the summer months but audiences have dropped off each year in the period since 2002.

Superman cost more than $200m (£109m) and hopes are high it will do well.

The film is released in the US on 28 June while the Pirates of the Caribbean sequel, another expensive release, opens on 7 July.

Revenues

To date, summer ticket revenues are $1.37 billion (£753m), up one percent on last year but down eight percent from 2004.

Audiences figures are down 14% on two years ago.

Early reviews for Superman Returns, directed by Bryan Singer and starring Brandon Routh, have been very positive.

"It deserves a budget and it deserves the scope we are bringing to it," said Singer.

Other big budget movies such as The DaVinci Code, X-Men: The Last Stand, The Break-Up and Nacho Libre, earned mixed reviews.

Summer films still to be released include Miami Vice, Lady in the Water and Snakes on a Plane.