WASHINGTON — Senator Clinton’s plan to pay for government matching contributions to retirement accounts with a higher estate tax puts her squarely at odds with the leading Republican presidential contenders, who all have vowed to kill off the “death tax” as part of their economic platforms. In the second-largest policy initiative of her presidential campaign, Mrs. Clinton is seeking to give every American a 401(k)-style retirement account, along with $1,000 in government matching contributions to millions in the working and middle class.

The plan carries a price tag of $20 billion to $25 billion a year, which Mrs. Clinton said she would offset with an inheritance tax for couples with estates at or above $7 million.

The Democratic presidential front-runner announced the proposal in a speech yesterday morning in Iowa in which she decried rising income inequality and a government under President Bush that she said had turned a “blind eye” toward people struggling to save enough money for retirement.

“Too many families in America today feel like they’re standing on a trap door. They’re just one diagnosis, one pink slip, one missed mortgage payment away from falling through and losing everything,” she said. “What’s been the Bush administration’s answer to these real-world problems? Well, it’s always the same answer: Help those with the most and good luck to everybody else.”

Under her proposal, all Americans would be able to create portable retirement accounts and contribute up to $5,000 a year in tax-deferred savings. For people earning less than $60,000 annually, the government would match the first $1,000 and would kick in up to $500 for individuals in the $60,000 to $100,000 income bracket.

“My plan will help tens of millions of middle-class families go from just getting by to getting ahead,” Mrs. Clinton said. She cited statistics showing a drop in the private savings rate to its lowest level since the Great Depression and said that under the Bush administration, the share of American workers with employer-provided retirement plans had fallen to less than 50% for the first time. As she did when she announced her sweeping health care proposal last month, Mrs. Clinton emphasized that people who are satisfied with their current retirement plan would not be affected. “No change is necessary,” she said.

But also like her health care plan, the focus from Republicans will be on the increased spending and taxes Mrs. Clinton is proposing, as well as a stepped-up role for government.

“It’s a troubling example of Senator Clinton’s belief that the government should have more power over your savings,” Kevin Madden, a spokesman for a Republican presidential candidate, Mitt Romney, said.

Like Mayor Giuliani, Mr. Romney has called for ending the estate tax, which Republicans have long referred to as the “death tax.”

Mrs. Clinton’s proposal would freeze the inheritance levy at the 2009 level of $7 million a couple, and her campaign cited a congressional estimate that continuing the tax would generate $400 billion over 10 years, well above the $25 billion estimated annual cost of her retirement account plan. The campaign said about 10,000 estates would be affected by the tax, against 50 million households that could potentially benefit from the federally matched savings.

The former first lady is also coming under fire from both Republicans and Democrats over her stance on Social Security. She has lambasted proposals to “privatize” the program, saying yesterday that it is “one of those ideas that deserves to be totally buried.” But unlike her Democratic rivals, she has resisted discussing specific solutions, such as raising the retirement age or hiking Social Security taxes, to save the trust fund from bankruptcy after the current projected depletion date of 2041. One Democratic opponent, Senator Dodd of Connecticut, said he was “stunned” by her evasiveness on the issue at a Democratic debate last week.

Her answer to what some have deemed a crisis in Social Security was the same yesterday as it was during the debate: a return to the “fiscal responsibility” that her husband demonstrated in the 1990s. She took a shot at critics whom she accused of exaggerating the problem.

“Don’t you believe all these people running around crying wolf about Social Security,” Mrs. Clinton said. “That is exactly what they’re doing. They’re trying to get people confused and upset and agree to a bad deal.”

She added: “I’m not going about demanding sacrifice from seniors and having others dismantle Social Security because they claim they can’t cut back on the tax breaks for wealthy Americans and big corporations.”

A campaign aide said she was referring to Republicans and the Bush administration, not the Democrats who have also criticized her approach to Social Security.

The Republican National Committee said Mrs. Clinton had painted an overly rosy picture of President Clinton’s record, pointing to a tax increase on Social Security benefits he signed in 1993. “If higher taxes and fewer benefits for seniors are what Senator Clinton looks to as a model for retirement security, it becomes obvious why she doesn’t want to answer questions about her own plans,” an RNC spokesman, Danny Diaz, said yesterday.

Mrs. Clinton’s Democratic competitors were mum on her retirement savings proposal, but the campaign of John Edwards took a dig at one element it did not include: a $5,000 “baby bond” program. Mrs. Clinton drew a frenzy of press attention — and criticism from Republicans — when she suggested the idea late last month. It was never an official program, and she told the Wall Street Journal on Monday that she would not push it. “Apparently, new polling data seems to have pressured the Clinton campaign to throw out the baby bond with the bath water,” a spokesman for Mr. Edwards, Chris Kofinis, said. The Clinton campaign declined comment.