NEW YORK (AP) - An independent group supporting Republican presidential candidate Mitt Romney says it's launching a multimillion-dollar advertising campaign in several general election battleground states.

People familiar with the plans say Americans for Prosperity plans to spend about $25 million on the ads beginning next week and running into early September. The ads will run in Colorado, Florida, Nevada, New Mexico, North Carolina, Ohio, Pennsylvania, Virginia and Wisconsin.

Americans for Prosperity was founded by David and Charles Koch (kohk), billionaire brothers who have contributed generously to Republican causes and candidates over the years. The group already has spent about $15 million in swing states this year on ads attacking President Barack Obama.