TOKYO — Nissan said on Wednesday that it expected its annual profit to be much lower than expected, a fresh blow to a company reeling from the arrest of its former top executive Carlos Ghosn.

The automaker told investors that its operating profit for the 2018 fiscal year, which ended in March, was expected to be 45 percent lower than the previous year, at 318 billion yen ($2.8 billion).

It was Nissan’s second downward revision in two months, highlighting the difficulties it faces as it moves past the fall of Mr. Ghosn, a corporate titan who was called in to right the company when it teetered on the brink of bankruptcy in the late 1990s.

Nissan said that weak sales in the United States, its largest market, and other regions had caused half of the slide in earnings, and that expenses related to extended warranties on vehicles sold in America had accounted for the other half.