Two dueling themes emerged as top executives from the world's carmakers gathered on the first day of the industry's annual showcase event -- the Detroit auto show.

The first is that a comeback in the U.S. auto industry appears to be under way and gaining traction. For proof, look no further than Ford Motor Co , which announced plans as the show opened on Monday to bring back 7,000 U.S. jobs over the next two years to meet resurgent demand for its vehicles.

But the second is a sense of continued caution among executives, fueled by what Bob Carter, Toyota Motor Corp's <7203.T> U.S. brand chief, calls the somewhat fragile state of consumers here -- nearly two years after the recession officially ended.

The U.S. auto industry snapped a four-year sales decline in 2010, including three consecutive sales months above the 12 million-unit annual rate to close the year. Most analysts expect double-digit growth in 2011 and further gains in 2012. The last time the U.S. auto market saw three consecutive years of substantial sales growth was in the late 1990s when Detroit automakers were still riding high.

Gasoline prices, however, are much higher today than they were back then and they are expected to stay that way. That helps explain why the show, which in past years often featured big, brawny, high-horsepower vehicles, is filled with smaller, more efficient vehicles this year.

Those include a slightly larger version of Toyota's market-leading Prius hybrid, the first-ever compact sedan for General Motors' Buick and a boxy concept known as the Curb from Hyundai Motor Co. <005380.KS>

Despite the tone of renewed confidence in some quarters that the industry and economy have turned the corner, the mood of this year's show was more subdued than in previous years.

Chrysler, for instance, had been known for spending heavily under its prior owners Daimler AG and Cerberus Capital Management on elaborately staged events to unveil vehicles at the Detroit show.

Past stunts included driving a Jeep through a glass window and herding dozens of longhorn cattle through the downtown streets.

But in its second show under the control of Italy's Fiat SpA , Chrysler was more restrained.

The ceiling of the company's exhibit was decorated with catchphrases brainstormed by its designers as a way to maintain morale during the crisis that had threatened Chrysler's survival prior to the 2009 bailout of the company by the Obama administration, including Cars can be fuel efficient without being neutered.

Chrysler used the Detroit auto show -- the industry's largest -- to showcase a redesigned and re-engineered version of its 300 sedan as well as a revamped mid-size sedan now known as the 200 and a refreshed version of its minivan.

I think we've proved over the last 19 months what this group can do, Fiat head Sergio Marchionne said. A lot of people were incredibly skeptical about our ability to launch all of these products within a short period of time.

MORE VEHICLE DEBUTS

In the first big event of the show, the Chevy Volt, the plug-in vehicle that has become the centerpiece of General Motors' return from bankruptcy and has already won both Motor Trend Magazine's car of the year and Green Car of the Year awards, was named 2011 North American Car of the Year award, beating out rival vehicles from Japan's Nissan Motor Co Ltd <7201.T> and Korea's Hyundai.

The latest version of Ford's Explorer sport utility vehicle, meanwhile, was named 2011 North American Truck of the Year -- the third year in a row that Ford has dominated the category. The new Explorer is built on a car platform, which improves ride and handling and offers much better fuel economy than the old Explorer.

The popularity of Ford's vehicles is prompting the company to bring back thousands of workers -- though many will be brought on at lower wages than the workers who were laid off in recent years, a reflection of the wrenching restructuring of the industry that is still, in many ways, under way.

The U.S. sweep of the awards, which are voted by a panel of 49 automotive journalists, provided an encouraging auto show kickoff for Detroit's Big 3 automakers. The show is the first in a string of trade events where automakers clamor to build buzz for vehicles months before they hit showrooms.

One sign of the industry's renewed confidence: vehicle debuts are expected to roughly double at the Detroit auto show this year to as many as 40 all-new vehicles, up from 18 in 2010.

Another major theme: the rollout of new small cars, electric vehicles and hybrids that major automakers have readied at a time when oil prices -- and gasoline prices at the pump -- are heading higher.

The Detroit auto show also represents a major milestone for Volkswagen. The German automaker plans to show off a new version of its Passat that will be built at its new U.S. plant. The $1 billion plant in Chattanooga, Tennessee, is near completion and will begin operations later this year, giving the automaker its first U.S. plant since the 1980s.

The Detroit show is also significant for the U.S. automakers, which are in varying stages of a comeback in sales and in profitability.

GM completed its public share offering in November, the largest ever, and its shares are up 18 percent from the IPO price. Chrysler is expected to launch its own IPO in the second half of 2011.

Ford passed Toyota as the No. 2 U.S. automaker in sales behind GM in 2010 and its stock has risen more than 80 percent since the start of last year.

Ford posted a 19 percent U.S. sales gain in 2010, its largest percentage increase since 1984. Ford shares were up 1 percent at $18.46 and GM shares were down 0.4 percent at $38.81 on Monday afternoon.

A KPMG survey found a much higher percentage of senior automotive industry executives expects global market share growth from Ford than Toyota in 2011.

Ford in one year essentially eclipsed Toyota, which is a big change in one year, said Gary Silberg, who leads KPMG's auto consulting business in the United States.

After massive recalls and U.S. market share losses in 2010, Toyota aims to turn the tide by expanding its Prius hybrid into a family of vehicles in a bid to enhance consumer perceptions that the automaker is a leader in green technology.

(Reporting by David Bailey; Additional reporting by Kevin Krolicki, Bernie Woodall, Deepa Seetharaman, James Kelleher and Chang-Ran Kim in Detroit, and John Crawley in Washington; editing by Matthew Lewis)