JOLIET, Ill.  A top General Motors executive said Thursday that automakers were “deserving” of as much as $50 billion in government-backed loans so that they can build more fuel-efficient cars.

G.M.’s vice chairman, Robert A. Lutz, said the car companies need money to retool their plants but probably cannot raise enough capital on their own because of the tight credit markets. He said the automakers have already made considerable progress in transforming themselves and that the government should help them proceed faster.

“The American auto industry is deserving of government loan guarantees,” Mr. Lutz told reporters at an event near Chicago where G.M. showed off its 2009 lineup. “We have done a whole bunch of things that people said, ‘Why aren’t you doing this?’ ”

The automakers, along with the United Automobile Workers union and Michigan lawmakers, are urging Congress to appropriate $3.75 billion to back the $25 billion in loans authorized last year.