Will Smith insists details of 'Suicide Squad' will remain a closely-guarded secret.

The 46-year-old star is set to appear in the much-anticipated movie based on DC comicbooks alongside the likes of Jared Leto and his 'Focus' co-star Margot Robbie, but says he's not able to reveal any information about the film before its release.

Asked whether he could speak about the 'Suicide Squad' movie, Will told BANG Showbiz: ''No sir, I'd have to kill you. It's top secret but it's really good, though. It's great stuff, fantastic. I'm already in shape for it, I'm already training.''

However, Will was more forthcoming about the plot of 'Focus', in which he plays a veteran con artist called Nicky, who takes a novice named Jess - who is played by Margot Robbie - under his wing and falls in love with her.

Speaking at the UK premiere of the film in London's Leicester Square, he explained: ''The [question of whether the character is good or evil] is one of the things that was interesting. I think he's injured a little bit. He's had a couple of really bad experiences and a rough upbringing.

''At his heart, he's a good guy. I think that's part of what's fun about the whole con aspect of the film.

''Even until the end of the film, the audience is not sure, and it's only in the final moments of the film that you get to make a decision about whether he's a good guy or not.''