Washington - US lawmakers were close to agreement Tuesday on a 15-billion-dollar bail-out for the US car industry, but some conservative legislators were still balking at the idea of the federal government rescuing a failing industry.

The package being considered is less than half the money that General Motors Corp, Chrysler LLC and Ford Motor Co have sought from Congress. It contains a series of tough conditions including the creation of a White House "car czar" to oversee their restructuring.

The White House and majority Democrats in Congress reached a deal "in concept" on the bail-out Tuesday night, according to a government official cited in the Washington Post. The final language was still under discussion, and it was unclear if enough Republican senators were on board for the bill to pass.

GM and Chrysler have both said that they will likely declare bankruptcy unless federal aid comes soon, blaming a drop in US car sales to 25-year lows amid the ongoing recession.

The US government has refused to intervene without congressional action, and legislators have been skeptical about saving an industry they considered slow to modernize.

US Senate majority leader Harry Reid, the upper chamber's top Democrat, said Tuesday that a vote could come as early as Wednesday, but he later suggested lawmakers may have to remain in session through the weekend.

Dana Perino, press secretary for US President George W Bush, said that the executive and legislative branches were making "good progress" on the bail-out package, but that "a number of issues" remain to be worked out.

The legislation would require carmakers by March 31 to show they had a viable, long-term plan for recovery, or the money could be taken back, according to the Washington Post.

The rescue would keep GM and Chrysler afloat long enough for president-elect Barack Obama's administration and a new Congress to re-evaluate the situation soon after the January 20 inauguration.

But some Republicans earlier Tuesday said the bill did not do enough to preclude another bail-out in future.

"We should demand that management make the tough choices that are required for long-term viability," said Mitch McConnell, leader of the Senate Republicans.

Barney Frank, the Democratic chair of the House Financial Services Committee, said that the White House and lawmakers from both parties agreed in principle that a bail-out was necessary.

"I don't see any outstanding issues over which it breaks up, but there are different ways of doing things," Frank told reporters.