ROANOKE, Va. -- Democratic presidential candidate Barack Obama yesterday sought to undercut Republican rival John McCain's support among older voters, warning that Mr. McCain wants to cut Medicare to pay for other plans.

Mr. McCain, whose aides said Mr. Obama was distorting facts to scare seniors, called the Democrat's tax plans "welfare" and argued that policies he is promoting as middle-class are more akin to socialism.

Mr. Obama delivered his message while campaigning in conservative southwest Virginia, but he intended for it to be heard in other battleground states, including retiree haven Florida, where Mr. McCain was making two appearances.

"When you've worked hard your whole life, and paid into the system, and done everything right, you shouldn't have the carpet pulled out from under you when you least expect it and can least afford it," Mr. Obama told a crowd of more than 8,000 gathered at the civic center in Roanoke, a Democrat-friendly city of 91,000 in a largely Republican part of the state.

Mr. Obama cited a figure of $882 billion in Medicare cuts over a decade, drawn in part from a study by the liberal think tank Center for American Progress. He said Mr. McCain was considering "drastic" cuts in Medicare equivalent to a 20 percent or more cut in benefits next year.

"It would mean fewer places to get care, and less freedom to choose your own doctors," Mr. Obama said. "You'll pay more for your drugs. You'll receive fewer services. You'll get lower quality care. I don't think that's right. In fact, it ain't right."

McCain senior policy adviser Doug Holtz-Eakin said Mr. Obama's criticism was false and "an attempt to simply scare American seniors." He said the kind of Medicare cost cuts the Republican nominee wants to make are in areas such as curbing fraud and unnecessary subsidies, slowing the growth of premiums and expanding generic drugs and chronic disease management. "No service is being reduced," Mr. Holtz-Eakin said.

Mr. Obama didn't mention Mr. McCain's promise of a $5,000-per-family health-care tax credit, but criticized the Republican's proposal to tax employer-provided health care.

Mr. Obama also sought to answer Republicans' suggestions that his own plans to expand health care would limit people's insurance options. "If you've got health insurance, the only thing that will change out of my plan is we will lower your premiums," he said.

It was Mr. Obama's seventh visit to southwest Virginia, but the Roanoke Times newspaper said it was the first time a major-party presidential nominee had campaigned in the city since John F. Kennedy in 1960. Virginia hasn't voted for a Democratic presidential candidate since 1964.

Mr. Obama continued to use local supporters to help sell him in the state's Appalachian region, where he did poorly in the state's February Democratic primary, although he won statewide. Sen. Jim Webb, D-Va., told the audience in Roanoke, "They say, 'That person's not like you, that person doesn't understand you,' " but "Barack Obama is like you. He knows what it's like to struggle."

Mr. Webb said much has been made of "certain ethnic issues," but while Mr. Obama's father was born in Kenya, his mother was from "Kansas by way of Kentucky." Mr. Webb said that if Mr. Obama were elected, he would be the 14th president whose family ties go "back to the mountains of this area."