The biggest shopping day in China is fast approaching, and American companies are treading carefully.

Nov. 11, known as Singles Day or Double-11, started as an anti-Valentine’s Day celebration before the Chinese e-commerce giant Alibaba Group converted it into an annual shopping spectacle that generates billions of dollars in sales. This year, Taylor Swift will help kick off the proceedings by performing at a gala in Shanghai. Some 22,000 international merchants are expected to offer discounts and other deals, mostly online, without the overnight lines and doorbuster bargains associated with Black Friday in the United States.

But American companies have seemed unsure of how to approach China’s $90 billion ad market, believed to be the second-largest in the world. The trade dispute with the United States has led some Chinese consumers to spurn American brands, and tensions over how companies have addressed pro-democracy demonstrations in Hong Kong have further complicated the economic back-and-forth.

Even before the disquiet, Chinese companies had overtaken many American rivals in spending on ads. In 2015, half the top 10 marketers in China were Western brands, with Procter & Gamble in first place, according to data from Magna, a media intelligence firm. Last year, three remained on the list, led by Coca-Cola in fifth place.