Washington  - Senator John McCain, 71, heads to the unlikely town of Sturgis, South Dakota, on Monday to rub elbows with the rowdy tattooed rebels of the American roads at a campground rock concert.

With a population of 780,000, South Dakota on the Great Plains is hardly an election-day prize for either McCain's Republican Party or rival Democrats.

But the state doubles in population during the annual August motorcycle rally in Sturgis, at the foot of the Black Hills, that draws an estimated 500,000 to 600,000 out-of-state "wild hogs" who roar cross country to celebrate their bike culture.

McCain plans to maximize on the crowds by providing the opening act at an annual concert that honours American military veterans at the Buffalo Chip campground, his campaign said Sunday.

McCain, the presumptive Republican presidential nominee, will warm up the crowd for performances by American Idol country music singer Kelly Pickler and the mercurial Kid Rock, according to the Sioux Falls Argus Leader newspaper online.

The annual motorcycle rally - from August 4-10 this year - is one of the country's largest, with a reputation for notorious and outrageous behaviour.

A novelty draw to the Buffalo Chip campground this year will be a firing range for cyclists to try out automatic rifles, including vintage World War I machine guns, camp owner Rod Woodruff told the Argus Leader.(dpa)