DETROIT — American automakers last year posted their best sales since the financial crisis, earning healthy profits from better products amid a steady increase in demand for new cars.

But the road ahead for General Motors, Ford and Chrysler will be crowded with tougher competition from foreign automakers, as the relatively healthy American car market becomes an even bigger draw, reported The New York Times.

Japan’s car companies are looking to rebound from natural disasters in Asia, and the debt crisis in Europe has automakers there looking to North America for more market share. Already, Nissan and Volkswagen have posted big sales gains in the United States for last year.

Even with increased demand, the Detroit companies will be hard-pressed to maintain their combined 47 percent share of the market, up from 45 percent in 2010, analysts said.

“It is not going to be an easy task,” said Jesse Toprak, vice president for industry analysis at the research Web site TrueCar.com. “They did benefit from the misery of others in 2011.”

Auto sales in the United States surged in December for the seventh consecutive month, as the industry continued its methodical comeback from the depths of recession.

Sales rose 8.7 percent in December, and increased 10 percent for all of 2011 compared with the previous year.

With about 12.8 million vehicles sold, it was the industry’s best year since 2008 — although still well short of the 16 million annual sales level enjoyed before the recession.

The biggest beneficiaries of the increased demand were G.M., Ford and Chrysler. All three companies reported increases in market share in the same year for the first time in two decades, according to the automotive-research Web site Edmunds.com, which began tracking share numbers in 1991.

Because of their restructurings — and in the case of G.M. and Chrysler government bailouts — Detroit was solidly profitable, a fact that President Obama has sought to use to his political benefit as he seeks re-election this year.

The continued comeback of new-vehicle sales underscored that the United States remained the most profitable car market in the world.

“It’s not the cash cow it once was, but it’s still a mature and profitable market, as opposed to more volatile emerging markets, or stagnant ones in Europe,” said Rebecca Lindland, an analyst with the consulting firm IHS Automotive.

Analysts said consumers were spending more freely on new vehicles because their current cars were aging and financing options were more readily available.

Mr. Toprak estimated that leasing accounted for 25 percent of sales in 2011, more than double the level of two years earlier.

The Detroit automakers all reported increases during December. Chrysler, which had lagged the market a year ago, said its sales jumped 37.1 percent from the year-earlier period on the strength of new Jeeps and sedans. Sales at G.M. climbed 4.6 percent during the month, and Ford reported a 10.1 percent increase.

Among the foreign manufacturers, Volkswagen said its monthly sales increased 31.4 percent, Hyundai posted a 13.3 percent improvement and Nissan reported a 7.7 percent gain. Toyota said its sales were flat in December, while Honda reported an 18.8 percent drop.

The research firm J. D. Power & Associates said December was the first month in which sales to individual consumers — a figure that excludes bulk deliveries to businesses and government buyers — topped one million since the August 2009 spike during the federal cash-for-clunkers trade-in program.

“The industry has managed through another series of external shocks and is in a healthier position as the year closes,” said John Humphrey, senior vice president for global automotive operations at J. D. Power.

Sales are expected to climb further this year. Edmunds.com is forecasting 2012 sales of 13.6 million, while TrueCar.com expects 13.8 million.

With the European economy floundering, most global automakers are putting more resources than ever into products for American consumers. Leading the way is Volkswagen, which introduced several revamped models last year and has big plans for more growth.

“We expect V.W. to be very aggressive in the U.S. market,” said Mr. Toprak. “Toyota and Honda will also likely gain back some of the share they have lost, but not all of it.”

Toyota and Honda lost sales last year because of supply constraints from the earthquake and tsunami in Japan as well as floods in Thailand. Their historic dominance in the small and midsize car segments also eroded because of the presence of more competitive models from the Detroit car companies.

Both Toyota and Honda vow, however, that their inventory problems are now behind them, and that a blitz of new products will lure shoppers back to their showrooms.

“I think we are extremely well positioned to show customers once again what we have to offer,” said Jim Lentz, head of Toyota’s sales operations in the United States.

A resurgence by foreign automakers will put pressure on the Detroit companies to hold on to their 2011 gains.

“We are forecasting for the Big Three all to lose some market share in the coming year,” said Ms. Lindland. “That’s not to say, however, that they won’t be profitable because they have restructured so dramatically.”

The American companies are hardly resting on their laurels, and will unveil a number of important new products next week at media previews of the annual auto show in Detroit.

G.M. is expected to show a new small Cadillac sedan and a little crossover vehicle from its Buick division. Chrysler plans to introduce the new Dodge Dart compact car, while Ford will take the wraps off a redesigned version of its midsize Fusion sedan.

There will also be plenty of foreign models competing for attention at the Detroit show.

“The selection of vehicles that consumers have to choose from is the best in the history of the U.S. industry,” said Mr. Toprak. “But it makes it that much harder for any one company to stand out.”