"We don't know," he said. "We just simply do not know. And we won't be able to know that for sure, I believe, until we're forced to walk down that road which is complicated and cumbersome."
Levin also said the sense of emergency in the room was palpable and added, "we cannot go home without attempting to get this done."
"It now goes to the actual stability of the financial sector itself," he said. "The banks and financial sector would be threatened if the Big Three go under."
Levin said using the Wall Street bailout money would be the "the clearest, cleanest, most certain path."
"The administration understands the importance of this problem and has the tools at its disposal."
Dodd said much the same thing after the hearing. "I don't think any of us want to play Russian roulette with that potential option. People are angry about bailouts. I suspect they would be a lot angrier about the failure of an automobile industry were literally thousands, hundreds of thousands of jobs could be lost."
"My preference would be that the Treasury and the Federal Reserve step up with the authority that we have given them," he said. "Their refusal to do anything about this at all is deeply disturbing. To put it mildly."
There were signs heading into Thursday that prospects for a bailout are grim, with both Senate Majority Leader Harry Reid, D-Nev., and Speaker of the House Nancy Pelosi, D-Calif., laying the groundwork for blaming the Bush administration if plans for the automakers collapse.
Reid said Wednesday there is not yet enough support among lawmakers to clinch the number of votes needed to tap into the TARP to pay for a bailout. At the same time, White House spokesman Tony Fratto said the administration remains "exceedingly reluctant" to tap into the $700 billion TARP funds to provide money for the auto bailout.
Jim Manley, Reid's spokesman, also said there really is no need for Congress to act.
"There is no reason to start at square one when [Treasury] Secretary [Henry] Paulson can protect millions of American jobs in one of our most important industries with the stroke of a pen today," Manley said.
"Sen. Reid remains committed to figuring out a way to help the auto companies avoid bankruptcy and prevent millions of Americans from losing their jobs. As we have said all along, the Treasury already has the authority and resources to protect thousands of Americans who work in our nation's struggling auto industry. If the administration continues to oppose using TARP funds to address this crisis, we will continue trying to find an alternate solution," he said.
Indeed, the leading bailout proposal in the Senate would not use TARP funds to bolster the industry. Instead, it would use $25 billion in loans Congress has already approved for the development of fuel-efficient vehicles.
Although there may be enough votes in the Senate to use that money, it could still run into trouble if, and when, the measure is subsequently considered by the House. Pelosi has said she is opposed to using that money for anything but fuel-efficient, environmentally friendly technology.
A recent CNN poll found about 60 percent of Americans oppose a bailout for the automakers.
ABC News' Vija Udenans and Charles Herman contributed to this report.