BILLINGS (Montana) - NEW Democratic running mates Barack Obama and Joseph Biden will head on their first joint campaign swing after this week's convention, a bus tour of battleground states, aides said on Wednesday.

The 'On the Road to Change' bus tour will leave the convention city of Denver Friday for Pennsylvania, with the candidates accompanied by their wives Michelle Obama and Jill Biden, according to a campaign statement.

The tour by the White House hopefuls will also take in Ohio and Michigan, two other rust-belt states that could prove pivotal to success in November's presidential election against Republican John McCain.

'Obama and Biden will meet with voters to discuss America's economic challenges and the Obama/Biden blueprint for change,' the statement said.

Aides have said that the two senators are likely to campaign separately after Monday's Labour Day holiday, which marks the start of the Republican convention in St Paul, Minnesota. -- AFP