Gwyneth Paltrow at the Glastonbury Festival in June

Proof, starring Paltrow and Sir Anthony Hopkins, will receive its North American premiere - as will Knightley's new version of Pride and Prejudice.

Diaz, meanwhile, will appear alongside Toni Collette and Shirley MacLaine in estranged sister comedy In My Shoes.

The festival, which runs from 8 to 17 September, will open with the Indian drama Water as previously announced.

In Proof, Paltrow plays the daughter of a maths genius, played by Hopkins, who fears she may have inherited his madness.

The film, which reunites her with Shakespeare in Love director John Madden, sees the actress reprise a role she played on stage in 2002.

Knightley is the latest actress to play Jane Austen's heroine

Other films playing at the festival include Ang Lee's gay cowboy drama Brokeback Mountain and Shopgirl, an adaptation of Steve Martin's novella starring Martin, Claire Danes and Jason Schwartzman.

Canadian directors David Cronenberg and Atom Egoyan will also present their films A History of Violence and Where the Truth Lies, both of which played earlier this year at the Cannes Film Festival.

"We all know that Cannes is terrific and fun, but this is the real festival," said Cronenberg last month.

"We go out to Cannes and we play and then we bring it back home."