By John Whitesides, Political Correspondent

ST. PETERSBURG, Florida (Reuters) - U.S. Democratic presidential candidate Barack Obama proposed a package of measures on Friday to help workers fight rising energy costs, including an immediate $1,000 tax rebate for low- and middle-income families.

Obama, trying to shift the focus of his campaign debate with Republican rival John McCain back to the economy, said he would pay for the $65 billion tax package with a 5-year windfall profits tax on oil companies.

The Illinois senator also revamped his proposal for a $50 billion economic stimulus plan to include $25 billion to replenish the highway trust fund and pay for infrastructure improvements that he said could save up to 1 million endangered jobs.

"With job losses mounting, prices rising, increased turbulence in our financial system, a growing credit crunch, we need to do more," Obama said at a town hall meeting in St. Petersburg, Florida.

The proposals came as the government announced the U.S. unemployment rate hit its highest level in four years with another 51,000 non-farm jobs lost in July, bringing job losses for the year to 463,000.

"Do you think you can afford another four years of the same failed economic policies?" Obama asked, accusing McCain of embracing President George W. Bush's economic approach.

The tax rebates, which would be phased out for those making more than $150,000 a year, are an accelerated version of Obama's earlier proposal for permanent tax reductions of up to $1,000 for working families, aides said.

"You can't afford to wait for relief. Right now, people are suffering," Obama said.