Critics of President Bush's (search) plan to create personal investment accounts in Social Security (search) say he is exaggerating the program's funding problems to boost public support for his idea.

"Social Security is like a car with a flat tire," said Peter Orszag, an economist at the liberal Brookings Institution and adviser in the Clinton White House (search). "There is a problem. We need to fix the flat tire. But we don't need to replace the car."

But David John, a senior analyst at the conservative Heritage Foundation, said the funding problem is real, especially for younger workers. "Every day we delay raises the cost of a repair to Social Security," he said.

The retirement system faces a projected $3.7 trillion, 75-year shortfall. Bush wants to overhaul the program to let younger workers divert some of their Social Security payroll taxes to personal accounts. But that alone won't fix the problem and could require upfront costs of $1 trillion to $2 trillion over 10 years.

Bush regularly claims Social Security faces a shortfall of nearly $11 trillion, which, Orszag said, is a misleading figure because it makes the system appear to be in worse shape than it is.

The figure — $10.4 trillion to be precise — is the shortfall over the "infinite horizon," as measured by Social Security's Board of Trustees. The calculation was included for the first time in the trustees' 2003 report, along with the required 75-year measure. The American Academy of Actuaries criticized the use of the $10.4 trillion figure in the report, saying it was likely to mislead the public.

Orszag said Medicare's dwindling finances are more urgent than Social Security's. Medicare began dipping into its trust fund this year, and it is expected to be exhausted in 2019, trustees said.

Social Security's financial picture was little changed from last year. The system is expected to begin paying out more in benefits than it collects in taxes starting in 2018, with the trust fund money the government owes depleted by 2042.

Rep. Bob Matsui of California, the top Democrat on the House Social Security subcommittee, said the retirement system is not in crisis and "is a manageable problem.

Bush, asked Monday at a year-end news conference about the need to address Medicare's funding problems first, said those issues were tackled with a sweeping Medicare package that includes a prescription drug plan being added in 2006 in addition to a number of lesser-known changes in the way the system operates. Depending on estimates, the government will spend from $400 billion to $535 billion on Medicare changes over the next 10 years.

Bush repeated his demand for congressional action on Social Security, but refused to provide details.

"Don't bother to ask me," he said, making clear he would not engage in a public debate about Social Security until he gives Congress "a solution at the appropriate time."

The administration has said a plan is still being crafted.

"The temptation is going to be ... to get me to negotiate with myself in public. To say, you know, 'What's this mean, Mr. President? What's that mean?' I'm not going to do that," Bush said. "The law will be written in the halls of Congress. And I will negotiate with them, with the members of Congress."

Bush continues to spotlight the Social Security's future financial problems and the positive aspects of his plan to allow people to create a retirement nest egg they own and mostly control — without raising the payroll taxes that fund Social Security or cutting benefits for retirees or those nearing retirement age.

Such a change comes with a cost: If money is diverted to private accounts, the government must replace it to continue paying benefits.

Bush has said benefits would not change for retirees and people nearing retirement, but he has not given age ranges. A commission he created in 2001 to study Social Security has proposed letting workers under age 55 open private investment accounts.

To help address the future long-term shortfall, a private account system would cut the government benefits promised to workers who choose a private account, with those investments expected to make up the difference.