The Medicare program is about keeping promises to millions of seniors who have put in a lifetime of hard work, President Barack Obama said Saturday in his radio and Internet address and in a new campaign ad. The president used his weekly address to discuss the surging campaign issue, saying his goal is to strengthen Medicare and preserve the program for future generations. He made no mention of Republican rival Mitt Romney in the address. But the new 30-second television ad says Romney "would break that promise" and replace the current Medicare system with a voucher program that wouldn't keep up with costs. "Insurance companies could just keep raising rates," the new ad says. Under a plan proposed by Romney's running mate, Rep. Paul Ryan, starting in 2023 Medicare would be radically changed. New retirees would get a fixed amount of government money to pick either private health insurance or a federal plan modeled on Medicare. Ryan says that would keep the program solvent. The Obama administration says the change could cost retirees as much as $6,400 a year. Romney has accused Obama of cutting more than $700 billion from Medicare to pay for his health care law. In the Republican's weekly address, Sen. Rand Paul of Kentucky said the nation is being hurt by "the looting of the Treasury and 20 years of deficit spending."