He said Tea Party Republicans have taken the political rhetoric "to a whole new level."
"They're threatening either to shut down the government or shut down the entire economy by refusing to let America pay its bills for the first time in history, unless I agree to gut a law that will help millions of people," Obama said Thursday in a speech in Maryland.
"That's not going to happen as long as I'm president. The Affordable Care Act is here to stay," he said.
The president said whatever effect the healthcare law might have on the economy, "it won't hurt the economy as bad as a government shutdown."
And as far as raising the debt ceiling, Obama said he will not negotiate on the issue. "We don't run out on our tab."
"This is not about the fortunes of any one party. This is not about politics. This is about the future of our country," he said. "If Republicans do not like the law, they can go through the regular channels and processes to try to change it. That's why we have elections."
"You do not threaten the full faith and credit of the United States of America."
Obama spoke Thursday morning before a crowd of about 1,800 at Prince George's Community College in Largo, Md.. The audience of young people is a key demographic the Obama administration is trying to reach in promoting the health insurance marketplace that will launch Tuesday at healthcare.gov.
Obama says young people in Maryland will find new options for insurance for as low as $100 a month when the program begins next week.
"In the United States of America, healthcare is not a privilege for the fortunate few. It is a right," Obama said. "Now, five days from now, five days from now, on October 1st, millions of Americans who don't have health insurance because they've been priced out of the market or because they've denied access because of a preexisting condition, they will finally be able to buy quality, affordable health insurance, in five days."
Obama highlighted the ease of the new program, which requires that insurers offer instant price quotes. "It's like booking a hotel or a plane ticket," he said
Obama said it appears the GOP's "biggest fear at this point is not that Affordable Care Act will fail. What they're worried about is it's going to succeed."
"You know, they have made such a big political issue out of this, trying to scare everybody with lies about death panels and killing Granny. So if it actually works, they'll look pretty bad. If it actually works, that will mean that everything they were saying really wasn't true and they were just playing politics."
He urged the crowd to spread the word that sign-up for the new program starts next week. "Tell your friends, tell your classmates, tell your family members," he said. "We need you to spread the word" about the law to counter the roadblocks set by "so many people out there working to make it fail."
Obama took an apparent swipe at billionaire brothers Charles and David Koch, who have bankrolled prominent ads against the healthcare law. "These are billionaires several times over. You know they've got good health care. But they are actually spending money on television trying to convince young people" not to sign up.
He said it appears House Republicans are thinking they need "to shut this thing down before people find out that they like it."
"Reforming health care's going to help the economy over the long term. Not only will it help lower costs for businesses, not only will it help families, it will free up entrepreneurship in this country, because if you've got a great idea for your own business, but you've never tried it because your spouse had a preexisting condition and you didn't want to lose your employer-based coverage, you've got the ability now to get your own coverage. That's security. That's freedom," he said.
Obama predicted Republicans will eventually come around, saying Medicare and Social Security faced the same kind of criticism.
"Before Medicare came into law, one Republican warned that one of these days you and I are going to spend our sunset years telling our children and our children's children what it once was like in America when men were free. That was Ronald Reagan. And eventually Ronald Reagan came around to Medicare and thought it was pretty good and actually helped make it better."
"So that's what's going to happen with the Affordable Care Act. And once it's working really well, I guarantee you, they will not call it 'Obamacare,'" he said.
Ohio bar shooting arrested, charged with murder
LGBT community has 'bullied the American people': Bachmann