The heads of the big three U.S. automakers are to testify before a U.S. Senate committee Thursday, to make the case for why the government should spend $34 billion to bail them out.

General Motors, Ford and Chrysler are reporting their worst sales in 26 years. GM and Chrysler say they may be out of business by February without government help.

But Senate Majority Leader Harry Reid, a Democrat, tells the Associated Press there are not enough Senate votes at this time to bail out the carmakers.

All three have submitted plans for rebuilding their businesses, severely hurt by the global recession, a lack of consumer credit, and selling large gas-guzzling cars many customers no longer want.

Along with promises to build more environmentally friendly hybrid and electric vehicles, the companies promise to cut jobs and slash executive pay and bonuses.

The United Auto Workers Union says it will renegotiate its contracts with the companies.

Union president Ron Gettelfinger said Wednesday that the union already has agreed to revise its health care plan and to suspend a jobs bank that required carmakers to pay laid-off workers. Gettelfinger dismissed criticism that an expensive union contract is to blame for the companies' downfall, saying the worldwide economic slowdown is the main cause.

U.S. President-elect Barack Obama supports a car industry bailout. But he said Wednesday that the companies must first present a viable long-term business plan.