The former Amercian Idol star, who released her second album Battlefield last month, will appear on the second US leg of the sell-out jaunt, kicking off in New York on August 24.
Further dates include Los Angeles, Boston, Philadelphia, Miami, Detroit and Chicago before concluding in Las Vegas on September 26 and 27.
"Britney's show is incredible and for me to be a part of it is a great opportunity," Sparks said in a statement.
Kristinia DeBarge will also perform at all US dates, while new acts Girlicious and One Call will appear in select cities.
'The Circus: Starring Britney Spears' continues to Australia in November.