Usher's sons are his ''most prized possession''.

The 'Scream' hitmaker is father to Usher, six, and five-year-old Naviyd - who he had with ex-wife Tameka Foster - and delights in the talents the two boys are already showing.

He said: ''They are definitely musical, Naviyd plays piano, he had his first recital not too long ago, but Usher is more active and athletic.

''They are my greatest investment, my most prized possession, it's everything.''

The 35-year-old singer portrays boxer Sugar Ray Leonard in new movie 'Hands of Stone' and loved working on the film - particularly as he learned how to fight and improved his physique.

Speaking on 'Live with Kelly and Michael', he said: ''I've been working on that for the last year and we just completed it. It's really incredible. I did train like a boxer, I'm actually rather good with my hands now.

''That's one of the great things about working on a boxing film, you definitely get the physique together, but greater than that was to act opposite Edgar Ramirez, Robert DeNiro, I mean, it was just incredible.''

Though he has an impressive body from making the movie, Usher admits to having a ''weakness'' for junk food.

Asked which of the coaches on 'The Voice' eats the most junk food, he admitted it was himself and added: ''My favourite junk food is Australian liquorice, I have a weakness.''