Washington ? Desperate U.S. automakers ran into fresh obstacles from skeptical lawmakers Thursday as they appealed with rising urgency — and a new dose of humility — for a $34 billion bailout. Without help, said one senator, “we’re looking at a death sentence.”

With lawmakers in both parties pressing the automakers to consider a pre-negotiated bankruptcy — something they have consistently shunned — the Big Three were contemplating a government-run restructuring that could yield results similar to bankruptcy, including massive downsizing, in return for the bailout billions. But there was no assurance they could get even that.

And that wasn’t all the unwelcome news. Congressional officials said one leading proposal — to tap an already approved fund set aside for making cars environmentally efficient — wouldn’t give the carmakers nearly as much money as they say they need.

The auto executives pleaded with lawmakers at a contentious Capitol Hill hearing — their second round in less than a month — for emergency aid before year’s end. But with time running out on the current Congress, skepticism about the bailout appeared to be as strong as ever.

“In all due respect, folks, I don’t think there’s faith that the next … three months will work out, given the past history,” said Sen. Charles E. Schumer, D-N.Y.

“No thinking person thinks that all three companies can survive,” said Republican Sen. Bob Corker of Tennessee.

Chris Dodd, chairman of the Banking Committee, was the senator who spoke of a death sentence — though he also said, “We’re not going to leave town without trying” to help.

The auto executives are to make their case at a House hearing on Friday, and Congress could take up rescue legislation next week in an emergency session.

But Democratic congressional leaders were leaning on the White House to act on its own. House Speaker Nancy Pelosi, D-Calif., and Senate Majority Leader Harry Reid, D-Nev., wrote to President George W. Bush on Thursday asking him, as they have repeatedly, to use the $700 billion Wall Street rescue fund to help the auto makers — something the administration has consistently refused to do. They argued that such a course was justified because of the potential for grave harm to the financial sector in the event of a carmaker collapse.

Auto state lawmakers went further, threatening to block the administration’s access to the second half of the financial bailout fund unless it made “a firm commitment to assist working Americans and save American jobs.”

The clear implication was that no more Wall Street aid would be available without help for the Big Three.

“I think they’ll read between the lines,” said Rep. Fred Upton, R-Mich., who teamed with Democratic Rep. John Dingell, also of Michigan, in a letter to colleagues outlining their position.