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President Bush pitched his newly remodeled Social Security (search) solvency plan to blue-collar workers Tuesday as the White House signaled that he wasn't wedded to a particular formula for reducing promised future benefits.

Bush's plan, which would allow benefits to rise the most for lower-income retirees, has drawn widespread Democratic and some Republican criticism since he unveiled it last Thursday at a prime-time news conference.

In his auto-plant speech, the president called the new indexing proposal an attempt "to help people come up with the solution" to Social Security's solvency problems. He said it would help the neediest retirees.

"That makes sense to me. I hope it makes sense to the U.S. Congress," Bush said.

His indexing plan "solves most of the long term problem," he added.

Earlier, White House spokesman Trent Duffy told reporters aboard Air Force One that the president wasn't troubled that the indexing plan (search) had drawn some GOP criticism and said that he was "open to all ideas."

"He has put out his proposal on a way to protect the lowest-level income workers. But in the context of the legislative process, he'll welcome other ideas to perfect or to make the best system," Duffy said.

The spokesman suggested that changes were to be expected as the measure goes through the legislative process. "The bottom line is, it is moving forward in both houses," said Duffy.

Bush spoke to about 2,000 workers at the sprawling, nonunion Nissan North America plant.

It was his first excursion outside the Washington, D.C., area since he added the benefit-indexing feature to his plan. In the past, Bush mainly emphasized his proposal to let workers under age 55 divert a portion of their Social Security payroll taxes into private investment accounts.

He promoted the personal account plan again in Tuesday's speech.

But, bowing to criticism that such private accounts would do little to fix Social Security's finances, Bush is now focusing his energy on an overhaul in which initial benefits would rise the most for low-income workers.

Proponents of the indexing plan say it would erase about 70 percent of Social Security's long-term deficit. Critics argue that the slower growth in benefits would fall hardest on middle-income Americans.

"I believe I have a duty as your president to talk about the problem and propose a solution," Bush said.

The president was angling to regain lost political momentum and reverse a slide in the polls. In addition to failing to build public support for his personal-accounts plan, Bush has been hurt by rising gasoline prices, turmoil over his nomination of John Bolton to be U.N. ambassador, the ethics problems of House Majority Leader Tom DeLay and backlash over involvement by the president and Congress in the Terri Schaivo tube-feeding case.

The president has also addressed an audience at a BMW auto plant in South Carolina.

"He hasn't overlooked the domestic auto industry," Duffy said. He said the president had invited workers from both Ford and General Motors to the White House for an event promoting development of hydrogen and other clean-fuel cars.

Greeting Bush at the airport were Mississippi Gov. Haley Barbour and Sen. Trent Lott, R-Miss. Sen. Thad Cochran, R-Miss., flew here with Bush aboard Air Force One.

Under Bush's revised plan, low-income workers would continue to have their benefits linked to the growth of wages, as now. The wealthiest seniors would have their initial benefits tied to price inflation, which usually rises more slowly than wages. For everyone in between, initial benefits would be figured by a sliding scale between price indexing and wage indexing. The White House has not said what income levels would trigger which benefit increases.