Several lawmakers in both parties, including Dodd, have pressed the automakers in recent days to consider a so-called "pre-packaged" bankruptcy in which they would negotiate with creditors in advance and downsize, then file for Chapter 11 protection in hopes of emerging quickly as stronger companies. The Big Three have publicly shunned the notion, but executives have indicated in recent days that it might ultimately be necessary.

GM's survival plan envisions an administration-led restructuring overseen by a government oversight board.

"If more extensive restructuring is required, GM will work with the oversight board to determine the additional necessary actions," GM's written plan said.

United Auto Workers union president Ron Gettelfinger told the committee, "We are prepared to do our part." But he also said workers for the auto companies shouldn't have to make disproportionate sacrifices.

He also said that any kind of bankruptcy, even a pre-packaged one, was not "a viable option." Gettelfinger claimed consuers would not buy autos from bankrupt companies, no matter the terms of the bankruptcy.

Congressional Democrats have urged the administration to tap into an already enacted $700 billion financial bailout program to help the auto industry.

The administration has said that it has no intention of doing so, and would prefer aid be taken from an earlier $25 billion program to help the industry retool its plants to make their vehicles more fuel-efficient.

Treasury Secretary Henry Paulson has said that the $700 billion program is intended only to be used for the financial industry.

Gene L. Dodaro, the top official at Congress' watchdog agency — the Government Accountability Office — agreed with Dodd that the $700 billion package set up in October "is worded broadly enough" to permit it to be tapped for the automakers.

Dodaro testified that the Federal Reserve also has the authority under existing law to make loans to the domestic auto industry if it so chooses.

Dodd said that both Paulson and Fed Chairman Ben Bernanke had been invited to testify at Thursday's hearing, but had declined.

Earlier, Senate Majority Leader Harry Reid, D-Nev., said prospects for Congress to act this year seemed slim.

"I just don't think we have the votes to do that now," he told The Associated Press.

Critics say the companies have been poorly managed and failed to show they won't be back for another government rescue.

In the streets outside the Capitol, all three companies were showcasing their futuristic, environmentally friendly models in hopes of counteracting their image as purveyors of gas-guzzling SUVs.

The three executives made the 520-mile trip from Detroit in hybrid cars — a nod to stinging criticism from lawmakers for making their last trip in corporate jets.

Congressional leaders have said Thursday's Senate hearing — and a companion one on Friday before a counterpart House panel — would help determine whether Congress will take up an auto rescue package in a special lame-duck session next week.