Justin Bieber is sick and is having a "chill" day to try and make himself feel better.

Justin Bieber has fallen ill ahead of his 'Believe' world tour.

The 18-year-old pop star is currently in the middle of promoting his most recent album of the same name and rehearsing for his mammoth run of concerts but it seems his hectic schedule has taken a toll on his health.

Writing on his twitter account, he revealed: "All the travel and the body finally broke down. Soo sick. Just gonna chill. #nofun (sic)"

Fans have since be tweeting get well soon messages to the singer, with one follower tweeting: "Get well soon #muchlove (sic)"

Before getting sick. Justin had been boasting to his followers that his tour was going to be his best live shows yet.

In a series of tweets, he wrote: "#BELIEVEtour is gonna change the game. im hitting every city. doing interviews. hitting the stage. WE READY! ... we have magic. #believetour

Justin - who is in a relationship with Selena Gomez - will start his 'Believe Tour' on September 29 in Glendale, Arizona, before heading across the US.

The 'Baby' singer then heads to Europe in 2013 and will be on the road until the end of March next year.