The opera singer is hoping to enjoy the ''challenge'' of the US TV dance contest - in which she will be partnered by Mark Ballas - but is unsure she can meet the physical demands.
She said: ''While I am so excited to be part of the show, I am a little nervous because I don't yet know what I am letting myself in for.
''This is something out of my comfort zone, it will be a challenge and hopefully something I will enjoy. I am ready for a challenge. I just hope I am physically up for the challenge.''
Katherine and Mark are starting rehearsals this week ahead of their stint on the show, with the dancer flying from the US to the UK especially to train with the 31-year-old beauty.
She told the New York Post newspaper: ''I start my first day of training tomorrow, Mark is coming over here for a week of rehearsals.''
Katherine will compete against famous faces including Tennis ace Martina Navratilova, singe Gavin Degraw, singer Gladys Knight and 'Melrose Place' actor Jack Wagner when 'Dancing with The Stars returns to US TV later this month,