WASHINGTON — The Senate today approved President Barack Obama's giant economic stimulus measure, part of a string of powerful government steps that could marshal close to $3 trillion in taxpayer and private money to revive the collapsing national economy.

The 61-37 vote by the Senate was a key victory for the president but sets up difficult negotiations with the House, which passed a slightly different version than the $838 billion bill approved today.

Both Pennsylvania senators, Robert Casey and Arlen Specter, voted for it.

Obama, who was in Fort Myers, Fla., promoting his economic rescue efforts, welcomed the vote as "good news. ... It's a good start."

It came shortly after the Treasury Department and Federal Reserve moved to commit colossal sums of money to help thaw credit markets and slow layoffs that have left 3.6 million Americans unemployed.

It was a historic day of emergency federal action, but Wall Street didn't seem impressed. The Dow Jones industrials were down more than 300 points in afternoon trading.

Treasury Secretary Timothy Geithner outlined few details of how the Obama administration would spend the remaining $350 billion of the $700 billion bank bailout program started last fall under President George W. Bush.

He also announced a new public-private partnership to help strengthen banks.