MANCHESTER, March 11 (Reuters) - Manchester United ( MANU ) plans to build a new 100,000-seat stadium next to the existing Old Trafford, the club announced on Tuesday.

"Today marks the start of an incredibly exciting journey to the delivery of what will be the world's greatest football stadium, at the centre of a regenerated Old Trafford," United's co-owner Jim Ratcliffe said in a statement.

The British billionaire had been open about his desire for a new, state-of-the art ground since he became a minority owner in February of last year, and the club had been studying whether to redevelop the existing stadium or build a new one.

The club unveiled architect designs for the new stadium at an event on Tuesday morning in London.