AC/DC will reschedule a number of shows on the upcoming fall US leg of the veteran hard rockers' globetrotting Black Ice Tour due to an unspecified medical procedure involving lead vocalist Brian Johnson.

Originally scheduled to kick off Oct. 1 in Phoenix, the opener and subsequent shows next month in Las Vegas; Louisville, KY; Kansas City, MO; Des Moines, IA; and Milwaukee, WI, will be rescheduled; the band has not yet issued replacement dates for those shows. A few dates that previously appeared on AC/DC's schedule, but for which tickets hadn't yet gone on sale, have dropped off the band's itinerary, at least for now. The impending tour leg will now kick off Oct. 16 in Washington, DC.

"Lead singer Brian Johnson recently underwent a medical procedure and at the advice of his doctor is taking some time to rest," the band posted recently at its official website.

"Black Ice," AC/DC's first new studio set in nearly a decade, surfaced last October. The album--sold in the US exclusively via Walmart, Sam's Club and the band's website--debuted at No. 1 in 29 countries, including the US.

AC/DC began the "Black Ice World Tour"--their first live shows in five years--last October.

According to the group's website, the Black Ice tour will hit Latin America following the forthcoming US dates, and then visit Australia and New Zealand "by early 2010."