Leonardo Dicaprio can't understand the plot of his new science-fiction movie 'Inception'.

The actor - who stars in director Chris Nolan's new film 'Inception', which is set to be released later in the year - said he struggled to understand the concept behind the movie which is based on the idea that a technology can enter dreams and extract information from people's minds.

He said: "I don't know where to begin, it's really hard. I don't know what I'm supposed to say about it, but it's Chris Nolan delving into dream psychoanalysis and also making a high octane, action-filled, surreal film that is all spawned from his mind. He wrote the entire thing, and it all made sense to him."

The 35-year-old Hollywood star admitted the complex film left him completely baffled at times.

He told the Daily Telegraph: "It didn't make much sense to us when we were doing it, and we had to do a ton of detective work to try to figure out what the movie was and what we were doing from day to day, but, thank god, we had somebody who knew what he was doing."