President Barack Obama on Monday pounded home the need for Congress to set aside petty differences and pass an $800-plus billion stimulus fund to fight an economic collapse not seen in 80 years.

In opening remarks at his first news conference as president, Obama again spoke of the dire state of the American economy and financial system and pushed Congress yet again to pass quickly the massive spending and tax cut measure.

"The federal government is the only entity left with the resources to jolt our economy back to life," he said.

Acknowledging that no one knew with certainty how to solve the economic crisis, Obama said he could say "with complete confidence that a failure to act will only deepen this crisis."

The president spoke in a nationally televised question-and-answer session with reporters.

When the stimulus bill passed the House of Representatives, not a single Republican voted for it.

On Monday an $838 billion version of the legislation cleared a crucial test vote in the Senate by a 61-36 margin, with all but three Republican senators opposing it.

Obama returned to the capital for the news conference from Elkhart, Indiana, where made a campaign-style pitch for the stimulus plan, having travelled on Monday to the hard-hit industrial city in hopes of winning support for the package that has become his first big test since taking office.

Obama participated in a town hall-style meeting in Elkhart and plans to hold another one on Tuesday in Fort Myers, Florida, and one Thursday in Peoria, Illinois.

All are cities that are suffering particularly hard times.