Cheap fuel prices are not deterring some automakers from building up their offerings of alternative fuel vehicles.

But the 50 percent fall in the gasoline price in the United States is making electrics and hybrids less competitive with gas-fueled cars, and making it harder for companies to boost investment in alternatives in a market that is back in love with guzzlers.

General Motors and Hyundai both took a stand at the North American International Auto Show in Detroit on Monday toward a lower carbon future, but few others followed suit.

GM doubled down on its position in the electric car market, unveiling a new 200-mile (320-kilometer) Chevrolet Bolt to challenge Tesla, and a snazzy updated Volt.

The Bolt, still in concept form but envisioned for a 2017 debut, is a small crossover that lowers the price of entry to a full-range electric to $30,000, after government incentives.

GM chief executive Mary Barra called the Bolt "a real game-changer" in the electric vehicle market.

"This is truly an EV for everyone," she said, implicitly contrasting the Bolt with Tesla's best-selling, 265-mile range Model S, a larger, luxury electric with a base price of $70,000.

GM also launched an improved model of the Chevy Volt, its plug-in hybrid that, while remaining the best-selling US electric since it was brought to market four years ago, has still not captured a mass audience.

The new Volt boosts the range on the electric engine alone to 50 miles from the previous 38, and, with both electric and gas engines engaged, has a much faster acceleration than before.

"Owners wanted to see a greater range on the new model, and we have delivered," said Barra.

Hyundai introduced its standard hybrid and plug-in hybrid Sonatas at the show, as it pushes ahead with an all-technologies strategy for the US and global market.

"While low fuel prices are the hot topic right now, we all recognize the long-term need to reduce CO2 emissions," said Mike O'Brien, Hyundai vice president of corporate and product planning for North America.

"We intend to lead the way to this more efficient future."

The climb to that future, though, has become steeper with the plunge in gasoline prices.

"There has been a shift in consumer preferences nationwide for three months now. That shift from small crossover mid-size and compacts migrates to large trucks, SUVs and utilities and even to luxury vehicles," said Alec Gutierrez, an industry analyst at Kelley Blue Book.

"This trend is sustainable because there are expectations that gas prices are going to stay low at least for another six months."

At the same time, said Gutierrez, another dynamic is working: manufacturers have incorporated new fuel-saving technologies in their traditional combustion engines, making them more competitive with hybrids and electrics.

- Government pressure -

Nevertheless, all automakers are under the pressure of tough government targets to raise their average fuel efficiency of their fleets to 54.5 miles per gallon (4.2 liters per 100 kilometers) by 2025.

That forces all to come up with alternative fuel versions of their most popular cars, even if they don't work for the market, price-wise.

Industry specialists say the cost of reaching the 2025 goals is huge to car builders, and that they are beginning to push back against the government over the tight deadline.

"The regulators are going to have to come to terms with these lower oil prices," said Martin Zimmerman, a professor at the University of Michigan and former head economist at Ford.

But the targets won't be rolled back completely.

"We have to electrify many of our cars to satisfy the requirements," said Audi head of sales Luca de Meo.

Mercedes Benz chairman Dieter Zetsche said more companies are coming out with less fuel-efficient SUVs in part because buyers are less concerned about fuel costs.

But he acknowledged that the industry has to improve, because Europe and even Asian countries are pressing them on CO2 emissions, in addition to the US fuel targets.

"At the end of the day, we will not have sufficient oil," said Zetsche.