WASHINGTON — Imperiled automakers and their union worked feverishly Wednesday to sell a skeptical Congress on a $34 billion aid plan, promising labor concessions and restructuring. The Senate's Democratic leader said there still weren't enough votes to tap the $700 billion federal bailout fund to prop up the foundering Big Three.

One day before the chiefs of the auto companies return to Capitol Hill to make their urgent cases for loans, Sen. Harry Reid, D-Nev., said the money was unlikely to come from the Wall Street rescue fund.

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

The White House called the timing of his comments "interesting" coming on the eve of high-stakes congressional hearings Democrats demanded.

"It's not hospitable," said Dana Perino, the White House press secretary.

In Capitol Hill meetings, industry officials said the collapse of one or more of the Big Three carmakers could greatly worsen the nation's recession and undermine the companies' ability to survive.

"We're on the brink with the U.S. auto manufacturing industry. We're down to months left," Chrysler's vice chairman, Jim Press, told the AP in a separate interview. "If we have a catastrophic failure of one of these car companies, in this tender environment for the economy, it's a huge blow. It could trigger a depression."

The United Auto Workers union, scrambling to preserve jobs and benefits, agreed at an emergency meeting in Detroit to allow the companies to delay payments to a multibillion-dollar, union-run health care trust and to scale back a jobs bank in which laid-off workers are paid most of their wages. The concessions could help mollify some lawmakers who have criticized the union's benefits as too rich when compared with those of workers at foreign-brand auto plants in the U.S.

The Bush administration and auto-state Republicans and Democrats are pushing to help the automakers with aid from a different source: a previously approved $25 billion program that's supposed to be used to help them produce more environmentally advanced vehicles.

Environmentalists — and a number of powerful friends in Congress — are vigorously opposing that idea.

Reid said the administration could act unilaterally to use a portion of the Wall Street bailout program for loans to the automakers, but the White House has consistently resisted that approach.

"There's talk going around now that the Bush White House may ask for" the second $350 billion installment of the $700 billion financial industry rescue fund, Reid said.