US President Barack Obama will make an unusual try to upstage his rival Mitt Romney's formal nomination by his party next week by launching campaigns in key battleground swing states, the Obama campaign announced on Wednesday.

The Obama campaign said the sitting Democratic President will be holding campaign events in Iowa, Colorado and Virginia during a two-day tour next week when Republican National Convention in Tampa, Florida is expected to draw a lot of attention.

Supporters listen as Barack Obama speaks during a campaign event at Canyon Springs High School in Las Vegas, Nevada August 22, 2012. [Photo/Agencies]

"We know this is a close election and we need to compete for every vote that we can compete for," said Obama campaign spokesperson Jennifer Psaki.

Vice-President Joe Biden and First Lady Michelle Obama will also make prominent public appearance during the GOP convention week. Biden plans to hold a rally in Tampa, Florida next Monday when the GOP convention kicks off.

Iowa, Colorado, Virginia and Florida are among the key battle ground swing states in this year's campaign, where Obama clinched in 2008 but Mitt Romney is definitely trying hard to win back.

Michelle Obama will land a big gig on "The Late Show with David Letterman" next Wednesday, her third appearance on the leading late night talk show, just a day before Romney formally accepts the party's presidential nomination, CBS announced on Wednesday.

Presidential candidates usually would stand down during their opposing party's political convention.