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President Obama blanketed the airwaves Sunday in a bid to sell his health care plan to the American people and put pressure on Congress to pass comprehensive reform legislation in the coming weeks.

As part of the blitz, the president appeared on the ABC, CBS, NBC and CNN Sunday shows, and on the Hispanic network Univision.

Obama also is visiting David Letterman on Monday, the first appearance ever by a sitting president on Letterman's "Late Show."

The campaign comes less than two weeks after he delivered an address to a joint session of Congress on his outline for health care reform.

The president's intense exposure drew early criticism Sunday. South Carolina Republican Sen. Lindsey Graham joked on NBC's "Meet the Press" that Obama has appeared everywhere except the Food Network. Graham said the current plan has the same likelihood of passing as a "snowball's chance in hell" despite the media blitz.

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But Obama used his platform to hammer key points of his proposals and beat back criticism.

On ABC's "This Week," Obama unequivocally rejected the notion that a health insurance mandate amounts to a tax increase. Obama backed a requirement for almost all Americans to buy health insurance in his address to Congress, and a provision requiring people buy insurance or pay a fine is part of Senate Finance Committee Chairman Max Baucus' legislation, which could be the blueprint for a health care deal.

Critics have raised concerns about the mandate, though, and Obama was pressed on whether it is tantamount to the kind of tax increase he pledged to avoid during the campaign.

"That's not true. ... My critics say everything's a tax increase. My critics say that I'm taking over every sector of the economy," Obama said. "I absolutely reject that notion."

Obama said other elements of the plan would make insurance affordable for people, from a new comparison-shopping "exchange" to tax credits.

"What it's saying is, is that we're not going to have other people carrying your burdens for you anymore," said Obama. "Right now everybody in America, just about, has to get auto insurance. Nobody considers that a tax increase."

Auto insurance, however, is widely mandated so that drivers carry liability insurance -- or insurance to cover damage to others. Obama's health insurance mandate would be imposed so that people cover their own expenses.

Obama faces an enormous political and communications challenge in selling his health care plan as Congress debates how to pay for it all.

He told CBS' "Face the Nation" that he will keep his pledge not to raise taxes on families earning up to $250,000, and that much of the final bill -- hundreds of billions of dollars over the next 10 years -- can be achieved from savings within the current system. Coming up with the rest remains a key legislative obstacle.

Obama put his support behind the idea of taxing employers that offer high-cost insurance plans.

"I do think that giving a disincentive to insurance companies to offer Cadillac plans that don't make people healthier is part of the way that we're going to bring down health care costs for everybody over the long term," Obama said on "Meet the Press."

Obama's network interviews were taped Friday at the White House. He became the first president to appear on five Sunday network shows in the same morning, an extraordinary effort to build public support for his top domestic priority.

The goal is expand and improve health insurance coverage and rein in long-term costs.

Republicans countered Obama's message Sunday, charging that he continues to make promises he cannot deliver and is pursuing a "big-government plan" that does not enjoy broad support.

House Minority Leader John Boehner said on "Meet the Press" that he thinks the current proposals are dead, and repeated his call for the president to hit the "reset" button and pursue health care reform in a genuinely bipartisan way.

Obama said on the same show that he wants ideas from both sides of the aisle and that he also expects concessions from both sides of the aisle.

And he repeated his view that a controversial government-run insurance plan -- favored by the left, despised by the right -- should be a "part of this," but should not be considered the "silver bullet" for health care problems.

Despite so many weeks of speeches, town halls and interviews, Obama said he has found it difficult at times to make a complex topic clear and relevant.

"I've tried to keep it digestible," Obama said. "It's very hard for people to get their arms around it. And that's been a case where I have been humbled and I just keep on trying harder."

Obama told Univision's "Al Punto" ("To the Point") that the strong opposition to his plan is part of a political strategy.

"Well, part of it is ... that the opposition has made a decision," he said. "They are just not going to support anything, for political reasons."

The Associated Press contributed to this report.