GREENVILLE, S.C. — President Barack Obama is launching his first ad defending his record on Medicare, accusing Republican Mitt Romney and running mate Paul Ryan of undermining the health care program critical to millions of seniors.

In a new ad released Friday, Obama’s campaign points to the AARP, which said in a letter to lawmakers earlier this year that Ryan’s plan to transform Medicare into a voucher-like system would lead to higher costs for seniors. It says Obama’s approach would strengthen the program.

Additional Photos

FILE - In this Thursday, Aug. 9, 2012 photo, President Barack Obama speaks at a campaign event at Colorado College, in Colorado Springs, Colo. Obama's campaign says Mitt Romney's selection of Wisconsin Rep. Paul Ryan as his running mate shows a commitment to "budget-busting tax cuts" for the wealthy and "greater burdens" on the middle class and seniors. (AP Photo/Pablo Martinez Monsivais, File) ASSOCIATED PRESS

Romney has criticized Obama for taking more than $700 billion in Medicare funds to help pay for the president’s health care law.

Obama campaign is running the ad in 8 states: New Hampshire, Virginia, North Carolina, Florida, Ohio, Iowa, Colorado and Nevada.