DEARBORN, MICH.: Ford Motor Co., which devoted itself for nearly 20 years to putting millions of Americans into big pickup trucks and sport utility vehicles, is about to alter its focus drastically and build more small cars.

The struggling automaker, reacting to what it sees as a rapid and permanent shift in consumer tastes brought on by high gasoline prices, plans to unveil its new direction on Thursday, when it will report quarterly earnings.

Among the changes, Ford is expected to announce that it will convert three of its North American assembly plants from trucks to cars, according to people familiar with the plans.

And as part of the huge bet it is placing on the direction of the troubled American auto industry, Ford will realign factories to manufacture more fuel-efficient engines and produce six of its next European car models for the U.S. market.

The company will also end speculation about its Mercury division by making the brand an integral part of its new small-car strategy, according to these people, who spoke on the condition that they not be quoted by name because of the timing of the official announcement on Thursday.

The sweeping changes are the result of months of strategic discussions by Ford executives, and represent a far-reaching response to the woes afflicting Detroit's automakers.

U.S. vehicle sales have slumped 10 percent so far this year, with Ford down 14 percent, and the industry is headed for its worst annual sales in more than a decade.

Moreover, $4-a-gallon gas and a weak economy have battered the market for big SUVs and pickups, and sent automakers scrambling to revamp their product lineups.

No company has more at stake than Ford, which popularized the SUV in the 1990s with its truck-based Explorer and led the boom in pickups with its best-selling F-series model.

After losing $15.3 billion in 2006 and 2007 combined, Ford had hoped to stabilize its operations this year and return to profitability in 2009.

But rising fuel prices and the collapsing truck market forced the company, the second-biggest U.S. automaker, to abandon its profit target in May and accelerate its shift to smaller
vehicles.

Since then, Ford's chief executive, Alan R. Mulally, has directed an unprecedented overhaul of the company's future products. Mulally, who joined the company from aircraft maker Boeing in 2006, is committed to reducing Ford's dependence on large vehicles, according to people familiar with his plans.

''We don't have a sustainable company if we don't do this,'' Mulally recently told members of his management team.

For at least a decade, about 60 percent of Ford's United States sales came from trucks and SUVs, compared to 40 percent from cars and car-based crossover vehicles.

Eight of the company's 14 plants in North America build trucks, SUVs and full-sized vans.

Those numbers are shifting rapidly as consumers turn away from large vehicles, and the chief goal internally is to make cars and crossovers the bulk of its product lineup to better align the company with market demand.