Robert Plant [ tickets ] and Alison Krauss [ tickets ] take their unlikely partnership on the road this spring, with the duo performing material from their surprise smash album, "Raising Sand."

The pair kicks off an extensive US and world tour April 20 in Louisville, KY, the first of four dates in this country, all of them set in southern cities. In May, the duo will head overseas for two weeks of European shows; details of the international itinerary can be found at the performers' shared "Sand" website.

More US dates are planned for June and July, according to Krauss' website.

Backed by a full band led by "Raising Sand" producer T-Bone Burnett, the duo will perform selections from their joint album, along with material from both artists' catalogs, according to Krauss' site.

According to a press release, the unlikely project came about when former Led Zeppelin frontman Plant phoned contemporary bluegrass star Krauss about seven years ago to tell her he admired her work and wanted to work with her someday. The duo first sang together at a Leadbelly tribute during Rock and Roll Hall of Fame induction ceremonies, and eventually enlisted producer Burnett to help them record together.

The resulting CD, "Raising Sand," debuted at No. 2 on The Billboard 200 album chart following its release last October, and was certified gold by the RIAA shortly after. The first single from the collection, "Gone Gone Gone (Done Moved On)," was nominated for a Grammy in the Best Pop Collaboration with Vocals category.

Country Music Television (CMT) will air a preview of the tour, "CMT Crossroads: Robert Plant [ tickets ] and Alison Krauss [ tickets ]," featuring performances of several songs from the album, on April 11.