Julian Bond, chairman of the N.A.A.C.P., and Dennis Courtland Hayes, its acting president and chief executive, said Mr. Bush should focus on addressing the underlying health care reasons that blacks have a shorter life expectancy than whites instead of citing it as a reason to support his idea of private accounts.

The administration has argued that the current Social Security system is a disadvantage to blacks, maintaining that with a shorter life span, they draw less than their fair share of lifetime benefits. Under Mr. Bush's proposal, money diverted from payroll taxes into personal retirement accounts, plus earnings on that money, could be passed along as an inheritance; under the current system, survivors of people who die before retiring sometimes do not receive Social Security benefits.

But an overhaul as envisioned by Mr. Bush would almost certainly entail a cut in the guaranteed benefits that the program has offered for seven decades.

"Rather than playing the race card to set Americans against Americans, we urge the administration to address the long-term problems the system faces now," Mr. Bond said. "Recognizing the shorter life expectancy of people of color is commendable, but placing them further at risk is no solution."

Government statistics show that the average life span of a newborn black male is 69, compared with 75 for a newborn white male. But critics of Mr. Bush's plan say black mortality figures are skewed by higher death rates among black infants and blacks' higher exposure to violent crime. They cite statistics showing that by the common retirement age of 65, life expectancy of black males becomes 79.6 years, compared with 81.6 years for while males.

"Don't use the fact that African-Americans have a lower life expectancy as an excuse for privatization," said Representative Elijah E. Cummings, Democrat of Maryland, a former chairman of the Congressional Black Caucus.

Mr. Bond, Mr. Hayes and Mr. Cummings were among speakers at a news conference that opened a lobbying effort to defeat the president's plan. The White House dismissed the criticism.

"President Bush does have a comprehensive plan that has greatly improved health, education, homeownership and economic opportunity for all Americans, including African-Americans," said a White House spokesman, Trent Duffy.

"The fact is that the current system penalizes some workers who don't reach retirement age, which is one of the many loopholes that can be fixed by bringing Social Security into the 21st century."

Mr. Hayes, though, said the creation of private accounts could bring reductions or changes in Social Security's survivor or disability programs.

"We have to be concerned about mutations," he said, "of changes that occur that we sometimes didn't foresee when we thought we were doing something good."

As examples, he said, constitutional amendments on behalf of blacks after the Civil War led to Jim Crow laws curbing black voting rights, and court decisions outlawing segregated schools led to white flight from cities and racial profiling in suburbs.