Two of country's biggest stars are joining forces for a U.S. tour early next year. Keith Urban and Carrie Underwood will hit the road together beginning Jan. 31 in a city to be announced. The outing will play 24 dates to be announced; tickets go on sale Dec. 1.

First, Urban will cap a hard-touring 2007 with North American dates through mid-December. He will also on Nov. 20 release the compilation "Greatest Hits: 18 Kids," via Capitol Nashville.

Underwood will be touring in support of her second Arista Nashville album, "Carnival Ride," which recently debuted at No. 1 on The Billboard 200. The "American Idol" winner's only other shows at present are a Nov. 16 appearance alongside top country names at the Oklahoma Centennial Spectacular in Oklahoma City and a May 4 set at the Stagecoach festival in Indio, Calif.