Washington ? President Barack Obama pushed back hard against Republican critics of his health care overhaul plan Monday, dismissing the “politics of the moment” marked by GOP comparisons of his efforts to socialism.

Struggling to revamp the nation’s $2.4 trillion health care system, the president gave ground on his tight timetable for passage of sweeping legislation.

Obama’s strong words came just hours after Republicans ratcheted up their criticism of the president and congressional Democrats. Michael Steele, chairman of the Republican Party, likened Obama’s plans to socialism and argued that the president, House Speaker Nancy Pelosi and key congressional committee chairmen are part of a “cabal” that wants to implement government-run health care.

The White House also faced troubling news in the latest polling, with approval of Obama’s handling of health care slipping.

“We can’t afford the politics of delay and defeat when it comes to health care,” Obama said after meeting with doctors, nurses and other health care workers at Children’s National Medical Center. “Not this time. Not now. There are too many lives and livelihoods at stake.”

Without mentioning his critic by name, the president recounted South Carolina Republican Sen. Jim DeMint’s comment that stopping Obama’s bid for health care overhaul could be the president’s “Waterloo,” a reference to the site of Napoleon’s bitter defeat in 1815.

“This isn’t about me,” Obama responded. “This isn’t about politics. This is about a health care system that is breaking America’s families, breaking America’s businesses and breaking America’s economy.”

Striking a more populist tone than in past remarks, the president complained that “health insurance companies and their executives have reaped windfall profits from a broken system.”

“Let’s fight our way through the politics of the moment,” Obama said. “Let’s pass reform by the end of this year.”

That reflects a shift in a timetable he has stressed repeatedly. Obama had said previously that he wanted the House and Senate to vote on legislation before lawmakers leave town for their August recess, with a comprehensive bill for him to sign in October.

“I want this done now. Now, if there are no deadlines, nothing gets done in this town,” Obama told PBS’s “The NewsHour.” “If somebody comes to me and says ‘It’s basically done, it’s going to spill over by a few days or a week,’ you know, that’s different.”

He said too much of the focus has been on what has not been accomplished instead of on a coalition of health companies, professionals and constituents. Later in the day, aides organized a conference call for Obama to speak with liberal bloggers and rally them behind the White House’s broad outline for overhaul.

“One of the things that I know the blogs are best at is debunking myths that can slip through a lot of the traditional media outlets and a lot of the conventional wisdom,” he said, according to audio of the call posted on Web sites. “And that is why you are going to play such an important role in our success in the weeks to come.”

Steele accused Obama of conducting a risky experiment that will hurt the economy and force millions to drop their current coverage.

“Obama-Pelosi want to start building a colossal, closed health care system where Washington decides. Republicans want and support an open health care system where patients and doctors make the decisions,” Steele said in a speech at the National Press Club.

Asked whether Obama’s health care plan represented socialism, Steele responded: “Yes. Next question.”

Obama has said he does not favor a government-run health care system. Legislation taking shape in the House envisions private insurance companies selling coverage in competition with the government.

The president is struggling to advance his trademark health care proposal after a period of evident progress. Two of three House committees have approved their portions of the bill, while one of two Senate panels have acted. A Washington Post-ABC News survey released Monday shows approval of Obama’s handling of health care overhaul slipping below 50 percent for the first time.

The president, who spent most of last week making his plea for health care overhaul, was pressing his case hard again this week, first at the children’s hospital, and later this week in a prime-time news conference Wednesday and a town hall in Ohio on Thursday.

Conservative Democrats have raised objections to some elements of the legislation, and Pelosi is floating an idea that could make proposed tax increases more palatable to them. She would like to limit income tax increases to couples making more than $1 million a year and individuals making more than $500,000, Pelosi spokesman Brendan Daly said Monday. The bill passed by the House Ways and Means Committee last week would increase taxes on couples making as little as $350,000 a year and individuals annually making as little as $280,000.