YOKOHAMA, Japan — Nissan warned on Tuesday that sales would continue to drop in major markets and forecast a sharp fall in operating profit, another blow for the automaker as it tries to shore up its management approach after the arrest of its former chairman Carlos Ghosn.

The company expects its operating profit to shrink nearly 28 percent, to 230 billion yen ($2 billion), for the fiscal year ending in March 2020. It blamed diminishing sales in the United States and Europe.

“We hope to hit the rock bottom in 2018 and 2019 and reverse the trend in the coming years,” the company’s chief executive, Hiroto Saikawa, told reporters.

Nissan said it expected to sell more cars globally as a result of expansion in the Chinese market.

Nissan and Renault continue to debate how best to manage their alliance, which accounted for 10.7 million car sales in 2018. The alliance, which includes Mitsubishi, has been struggling since Mr. Ghosn was charged with financial wrongdoing last year in Japan and later stripped of his positions by all the carmakers.