The singer pleaded not guilty to rape during a court hearing in November last year and is due to appear at Wolverhampton Crown Court on Tuesday.
Williams, who enjoyed chart success after shooting to fame on The X Factor in 2008, was arrested in December 2016 following allegations he had attacked a woman at a hotel.
The 32-year-old, of Croydon, south London, is due to stand trial with co-defendant Jamien Nagadhana.
Nagadhana, also 32, from Hounslow, west London, denies a charge of assault by penetration in connection with the same incident.
After the allegations came to light, Williams said he would be stepping back from charity work, adding: “Press speculation is likely to be unhelpful to the charities I work with.”