Republican presidential candidate former Massachusetts Gov. Mitt Romney and his wife Ann arrive for a town hall meeting at the Exeter Town Hall , Thursday, Nov. 3, 2011 in Exeter, N.H. (Jim Cole/AP)

Republican presidential candidate Mitt Romney said on Friday that he would lower the federal debt by transforming Medicare and Social Security and reshaping or eliminating other costly government programs.

Romney unveiled a blueprint to overhaul entitlement programs popular with seniors, saying he would gradually raise the retirement age for Medicare and Social Security. Under his plan, future retirees would have the option of staying on traditional Medicare or purchasing health insurance from private companies through “premium supports,” or vouchers.

Romney also said he would turn responsibility for Medicaid, the government health care program for the poor, over to state governments, and cut about $100 billion in Medicaid spending. He also would cap federal spending at 20 percent of gross domestic product by the end of his first term. To do so, he would cut about $500 billion in annual spending and lower non-defense discretionary spending to 2008 levels.

“The plan I propose to make government simpler, smaller and smarter represents the biggest fundamental change to the federal government in modern history. It’s a change we’ll have to make if the words full faith and credit of the United States are to mean anything at all,” Romney said in an address before more than 1,000 tea party activists in Washington at Americans For Prosperity’s “Defending the American Dream” convention.

Romney, a former Massachusetts governor, has yet to fill in key details for his plan to overhaul entitlement programs, but the broad framework is similar to the blueprint of House Budget Committee Chairman Paul Ryan (R-Wis.). Both programs allow seniors to use a voucher for private insurance, and they do not effect seniors at or near retirement. But unlike Ryan’s plan, Romney’s would give seniors the option of remaining in the traditional Medicare program. Romney said his plan would not effect seniors at or near retirement.

“The future of Medicare should be marked by competition, choice and by innovation — rather than bureaucracy, stagnation and bankruptcy,” Romney said, adding: “Tomorrow’s seniors should have the freedom to choose what their health coverage looks like.”

In a conference call Friday morning with reporters, Romney’s advisers sought to present Romney’s plan as “aggressive.” One top adviser called it “a bold vision, but it’s also a thoughtful and achievable vision.”

Romney’s proposal calls for cutting programs that cost the government money and that he believes are not necessary. He said he would start with repealing President Obama’s health-care overhaul, a pledge that was received with hearty applause. “Obamacare is bad law, bad policy, and when I’m president, the bad news of Obamacare will be over,” he said.

Romney also said he would reevaluate hundreds of millions of dollars in foreign aid commitments. “I will stop sending money to any country that can take care of itself, and no foreign aid will go to countries that oppose American interests,” Romney said. But he made clear he would reverse Obama’s cuts to the defense budget and spend more money on enhancing the Navy and Air Force.

In a 25-minute speech, which he delivered from teleprompters into a cavernous convention hall, Romney cast himself as an “old business guy.” Romney said he would apply solutions he learned in the corporate world to the government.

“When I get into the White House — hopefully — nobody will need to teach me how to balance budgets,” Romney said. “I’ve been doing that for 35 years.”

Romney contrasted his role helping found Staples, the office supply superstore, on the cheap with Solyndra, the energy firm with a California headquarters Romney said was known as “Taj Mahal.” Solyndra, which received a $535 million federal loan guarantee under the Obama administration, filed for bankruptcy and closed in August.

“Our headquarters was located in the back of an empty food warehouse,” Romney said. “We got some used office furniture — old Naugahyde chairs. You had to be an athlete to get out of them. Every penny we had went into selling the product and attracting new customers.”

Romney said he would cut the federal worker payroll by at least 10 percent, which he said would yield annual savings of about $3.5 billion.

“The American people are increasingly working to support the government,” Romney said. “It ought to be the other way around.”

Democrats and Romney’s GOP opponents sharply criticized his fiscal policy plan. The rival campaign of Texas Gov. Rick Perry preemptively attacked Romney’s plan with a video, “Romney: Believe in Bailouts,” arguing that Romney would prioritize the interests of the financial sector.

“While Mr. Romney continues to put Wall Street over Main Street, Rick Perry is a real fiscal conservative whose economic plan ends Washington and Wall Street bailouts, cuts taxes and federal spending and balances the budget by 2020,” Perry campaign spokesman Ray Sullivan said in a statement.

Meanwhile, Tim Miller, a spokesman for former Utah governor Jon M. Huntsman Jr.’s campaign, said Romney’s speech was “timid.”

“Mitt Romney’s speech was that of a typical politician, complete with a teleprompter,” Miller said in a statement. “He pandered to interest groups and offered timid reforms to government spending, all the while trying to convince voters he will magically balance the budget anyway.”

Romney faced fire from Democrats, too, who employed the same line of attack against his proposals that they used against Ryan’s plan. James Kvall, Obama’s campaign policy director, wrote in a memorandum to reporters that Romney would be “ending Medicare and Medicaid as we know them.” Kvall tried to cast Romney as a champion of the wealthy at the expense of those in the middle and working classes.

“Romney apparently operates under the false assumption that we can just cut our way to prosperity,” Kvall wrote, adding: “He would return American families to the failed economic policies that contributed to the years of rising inequality, stagnant wages, and eroding middle-class security.”