Reid and House Speaker Nancy Pelosi said in a press conference that the Big Three automakers -- Ford, General Motors and Chrysler -- had failed to convince Congress that they had developed a viable plan for the $25 million they are requesting in bailout funds.
"This is an important industry in our country and we intend to save it," Pelosi said. "Until they show us a plan we cannot show them the money."
Reid said Congress would return the week of December 8 to consider the proposal, but only if lawmakers are convinced that the public would be well-served.
The ultimatum was worked out in a closed-door meeting with House and Senate Democrats in Pelosi's office, the sources said.
It's not yet certain what kind of bipartisan support the plan would have.
On Wednesday, Reid reversed plans to hold a test vote on a automaker bailout bill.
A House Democratic leadership aide said a compromise had little chance in the House, whose members expect to leave town for the year on Thursday afternoon.
Reid had planned to have a vote on legislation that would have taken $25 billion from the $700 billion already approved for Wall Street and diverted it to the Big Three automakers. But an aide said he decided to hold the legislation when it became clear it would fall well short of the 60 votes needed to pass.
Reid did, however, make a procedural move that could allow a vote on a compromise, which several senators from auto-producing states are feverishly trying to craft.
Still, a Democratic leadership aide suggested the chances those senators could come up with something acceptable -- with the votes to pass the Senate and eventually the House -- are not very good. Reid himself acknowledged as much from the Senate floor.
"I understand the importance of this," Reid said. "But I would hope that in addition to understanding the importance of this, we have to face reality. And the reality is that we've tried a number of different approaches."
A senior House Democratic leadership aide said the outlook for a last-minute Senate compromise in the House would be grim.
Pelosi "has made clear that's not going to fly," the aide said.
The aide said "no one wants to say die" on trying to revive something before members leave town -- as they expect to do Thursday afternoon -- but it's "very unlikely" that will happen.
The Senate on Thursday is expected to take up a bill to extend unemployment benefits -- which the House approved in September.