and says federal authorities have seized powers not granted by the constitution, and believes US forces should be brought home from Iraq.

The Libertarian Party stands for non-interference by the US government in the personal and business lives of Americans, and advocates lower taxes, a smaller government and more individual freedom.

The 59-year-old said he was not concerned about the prospect of damaging McCain, possibly among conservative voters whom the Republican candidate has had trouble courting.

Independent and third parties have faced a tough task in modern US election history of breaking the dominance of the Democratic and Republican parties, though several candidates have played a spoiler role.

Many Democrats still blame consumer advocate Ralph Nader, who has already announced a 2008 run, for depressing former vice president Al Gore's vote in 2000, and helping George W. Bush to capture the presidency.