President-elect Barack Obama demanded bold action on his near $800 billion stimulus plan, warning Congress would send the US economy into an even deeper hole if it fails to act swiftly.

Obama touted a sweetener of $300 billion in tax cuts in an apparent bid for opposition Republican support, as he plunged into the fray on his first day since moving to Washington, two weeks before his inauguration.

"The most important message today is that the situation is getting worse, we've got to act boldly, and we've got to act swiftly. We cannot delay," said Obama who met leaders from both sides of the political divide on Capitol Hill.

"It's clear that we have to act and we have to act now to address this crisis and break the momentum of the recession, or the next few years could be dramatically worse," Obama said.

Obama sent a jolt of momentum through Washington after several congressional leaders on Sunday dismissed expectations that the mammoth stimulus plan could be on the new president's desk when he is sworn in on January 20. Mid-February is now the target date for action by both chambers of Congress.

The president-elect's aides meanwhile divulged details of the massive scope of the package, his opening political gambit as he takes office amid the worst global economic crisis for more than 70 years.

Obama will propose tax cuts totaling $300 billion over two years, or around 40 percent of a package that could top $775 billion, a transition source said on condition of anonymity.