WASHINGTON – Weary Democratic congressional leaders and White House officials agreed in principle Tuesday on a $15 billion bailout of U.S. automakers that would give the government extraordinary power to restructure the failing industry. But the rescue faced snags as Republicans raised deep concerns.

Congressional aides and a senior administration official said the proposed deal would speed the loans to Detroit’s struggling car companies and place a “car czar” named by President George W. Bush in charge of overhauling the auto industry. Congress could vote on the plan as early as today, and the money could be disbursed within days.

A breakthrough came when negotiators reached a compromise to require the czar to revoke the loans and deny any further federal aid to automakers that don’t strike a deal with labor unions, creditors and others to ensure their survival by next spring – essentially pushing them into bankruptcy.

“A great deal of progress has been made on auto legislation that will protect the taxpayer and ensure that short-term financing is available only to companies prepared to undertake the dramatic restructuring necessary to become viable and competitive,” Dana Perino, the White House press secretary, said late Tuesday.

Earlier in the day, Rep. Barney Frank, D-Mass., the Financial Services Committee chairman, said the remaining issues were minor.

“There do not appear to me to be differences in principle of a sufficient nature to blow this thing up,” said Frank, whose staff is helping to draft the bill.

Still, staff aides worked into the night fine-tuning the agreement. It could face substantial obstacles from congressional Republicans, who remained skeptical.

A further stumbling block was Democrats’ refusal to scrap language that would force the carmakers to drop lawsuits challenging emissions limits in California and other states. That measure “kills the deal,” said Dan Meyer, Bush’s top lobbyist.

Senior Democratic aides acknowledged as much Tuesday and said they expected the provision to be dropped.

Another remaining hang-up was over ensuring that Cerberus, the private equity firm that owns Chrysler LLC, would reimburse the government if the auto company defaulted on its loan, said a congressional negotiator who spoke on condition of anonymity because he was not authorized to disclose details of the talks.

But the White House and congressional Democrats resolved other major conflicts. Democrats said they were willing to toughen the measure to require that the czar revoke loans from car companies that couldn’t show they were viable by the end of March.

They were also near agreement to weaken a proposal to give the czar veto power over automakers’ business transactions. They were discussing giving the overseer say-so over transactions of $100 million or more, instead of $25 million.

The measure is expected to provide emergency loans to General Motors Corp. and Chrysler, which have said they could collapse within weeks absent federal help. Ford Motor Co. has said it doesn’t need an immediate cash transfusion, but wants a $9 billion line of credit.