WeChat is used by more than 1.2 billion people globally.

Photo: Andrew Harrer/Bloomberg News

SINGAPORE—U.S. businesses in China are pushing back against a looming Trump administration ban on Tencent Holdings TCEHY 1.73% ’ WeChat app, with a report Wednesday shedding light on just how vital the tool is to companies doing business in the world’s second-largest economy.

The American Chamber of Commerce in Shanghai warned of an “enormous negative impact” on U.S. companies with international businesses if the order, whose scope has yet to be revealed, was enacted too broadly.

The Chinese app, a ubiquitous chat messaging and commercial platform, has come under the spotlight as technology increasingly takes center stage in a confrontation between the world’s two major economies. On Aug. 6, President Trump issued an executive order banning U.S. individuals and firms from transactions involving WeChat, to be effective from late September, citing concerns over national security. The order has rattled American firms, concerned that the ban could be applied beyond the U.S. and in China.

AmCham Shanghai, which includes firms such as Coca-Cola Co. and JP Morgan Chase & Co. among its 1,400 members, surveyed more than 140 corporates this month.

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