Keira Knightley to play Robert Pattinson's lover in Cosmopolis

Keira Knightley will star alongside Robert Pattinson in 'Cosmopolis'.

The British actress will play the 24-year-old star's love interest in the David Cronenberg-directed film, based the Don DeLillo novel.

The pair are expected to get up close and personal with each other in the film, which shows 24 hours in the life of a billionaire financier who squanders his fortune and his new wife.

An insider said: "Keira will get to do a lot of smooching with Rob. Some of the scenes are going to be pretty steamy."

Marion Cotillard was originally lined up for the film's single female role - but now Keira, 25, is on board

in the movie's second big casting change after Irish star Colin Farrell backed out earlier this year.

Director David has nothing but praise for his new leading lady.

He said: "Keira is a brilliant actress. She blew everyone away. She's a real heavy dude. She's as good as anyone I've worked with.

"You don't realise it until you start to actually work with somebody."

'Cosmopolis' will be Robert's first major film after completing 'The Twilight Saga', in which he plays vampire Edward Cullen.

He will next be seen on screen in 'Water for Elephants', starring alongside Reese Witherspoon in the Francis Lawrence-directed adaptation of the Sara Gruen novel.