Even as analysts are forecasting declines in auto sales in the United States this year and next, Fiat Chrysler Automobiles believes the time is still ripe for expansion.

On Tuesday, the Italian-American automaker said it planned to spend $4.5 billion over the next three years to update several Detroit plants and retool an engine plant to make Jeeps, an effort the company said would create about 6,500 new jobs.

While moving forward, it also took a step back, trimming operations at an Illinois plant and eliminating almost 1,400 jobs.

The other big American automakers, General Motors and Ford, have been cutting jobs and production. But Mike Manley, Fiat Chrysler’s chief executive, said he was confident that the American economy would remain on track.