SAN FRANCISCO — Alex Lidow has sold semiconductors in China for decades, starting at a company, called International Rectifier, that his father and grandfather founded in the Los Angeles area in 1947.

Now Mr. Lidow runs Efficient Power Conversion, which makes chips that manage electrical power in cars and other products. Efficient Power has a strong foothold in China, but has lately run into resistance from customers there that he traces to moves in Washington.

Mr. Lidow is among the semiconductor executives in the United States who have become concerned that the trade war with China — particularly the Trump administration’s ban on selling chips to some prominent Chinese customers — won’t just squeeze current revenue. He fears that recent events have convinced Chinese companies that American component makers can no longer be seen as dependable partners and are permanently shifting away from them.

“In my 40 years in this business, I’ve had friends in China that viewed me as a trusted supplier,” Mr. Lidow said. “They can’t now.”