The 55-year-old played the role of John McClane in the original trilogy as well as the fourth flick, Live Free or Die Hard, which was released three years ago.
Earlier this summer Willis said that shooting on the movie was 'imminent' but he now admits this was wrong.
He said to MTV: 'I think I may have said the word wrong. I thought 'imminent' meant that you have a lot of 'em. So I have to apologise for that.'
He added: 'It's probably going to happen in 2011. We have a script. They're making a couple [of] changes right now.'