SHANGHAI—U.S.-China political tensions remain the top concern for American companies in China despite some optimism about the relationship improving under President Biden, according to companies surveyed by the American Chamber of Commerce in China.

Half of U.S. companies are pessimistic about the effect that the bilateral relations could have on their China business over the next two years, with only 16% of respondents expressing optimism, according to the chamber’s annual Business Climate Survey, which was published Tuesday in Beijing. The chamber surveyed 345 companies in October and November 2020.

The pessimism comes despite 50% of respondents predicting the tone of the U.S.-China relationship would likely improve this year following the change in leadership in Washington, up from just 30% of respondents last year who thought relations would improve.

“The relationship remains contentious,” Greg Gilligan, AmCham China’s chairman, said in an interview. The caution among U.S. companies reflects a belief that, under President Biden, “we’re returning to a more traditional bilateral relationship and diplomacy, but we’re not returning to a lower level of tension in the relationship,” he said.

China was the only major world economy to expand last year, and served as a lifeline for a range of large U.S. companies, including Starbucks Corp. , Nike Inc. and Tesla Inc., which reported growing sales in China even as its other markets were crushed by the pandemic.