LAS VEGAS - Democrat Barack Obama on Sunday unveiled an economic stimulus package costing up to $120 billion that his campaign said would put money in the hands of workers and seniors, stem the foreclosure crisis and cover state budget shortfalls.

"Obama believes we cannot wait until he becomes president to give workers the tax relief they need," according to a policy paper.

Obama, a senator from Illinois, called on the government to make available a $250 tax credit to 150 million workers to offset the payroll tax paid on the first $8,100 of earnings. He urged a further $250 tax credit per worker if employment declines three months in a row.

He also would give a one-time, $250 payment to Social Security recipients who would not benefit from the tax credit, followed by another $250 payment if employment declines three months straight.

The immediate relief would cost $75 billion, plus another $45 billion if the economy weakened.

Obama also pledged $10 billion to increase pre-foreclosure counseling and help "responsible homeowners" refinance their mortgages or sell their homes.

The plan also calls for $10 billion to help states and local governments facing budget problems as a result of the housing crisis, caused by falling property values and sales tax revenue.

Obama also wants $10 billion to extend unemployment insurance while loosening the eligibility criteria to include many part-time and nontraditional workers.

The plan would have to be approved by Congress and President Bush to go forward, which is not likely. But Obama's campaign said it represented the kind of relief he would pursue if he were president now.

Austan Goolsbee, a senior economic policy adviser to Obama, said the plan was slightly larger than the $110 billion package advocated by Obama's chief rival, Sen. Hillary Rodham Clinton, on Friday.

Goolsbee said Obama's plan would have a more immediate impact because checks for tax credits and Social Security payments could be issued right away, while Clinton's plan to subsidize such things as higher heating bills would require an application process.

"Those are things that would take many months if not a year or more before the money would get out the door," Goolsbee said. "If you're going to have fiscal stimulus, the absolutely most imperative thing is to get the money into people's hands immediately so that they can use it and prevent the slowdown."

The Clinton campaign noted her plan would offer more assistance on housing than Obama's — $30 billion in total — and touted her proposal to impose a moratorium on subprime-loan-based foreclosures and freeze subprime mortgage lending rates.

The Republican National Committee criticized both plans, calling Obama's a "knee-jerk tax-and-spend" proposal, while saying Clinton's reflected her "record of raising taxes to pay for bloated government programs."