U.S. companies based in the financial hub Shanghai said Washington's planned ban on Chinese messaging app WeChat could badly hit their competitiveness and revenue should it apply to U.S. firms and citizens in China, a survey showed on Wednesday.

According to the survey conducted by the American Chamber (AmCham) in that Chinese city, 88 percent of the 142 respondents from the firms subject to U.S. jurisdiction this week expected a negative impact on operations stemming from the loss of WeChat as a communication tool.

U.S. President Donald Trump this month announced an executive order banning WeChat-related U.S. transactions from mid-September citing national security. His administration is yet to detail the types of transactions affected. 

WeChat is operated by Tencent Holdings Ltd, one of China's biggest social media and gaming firms. It has clocked a relatively small 19 million downloads in the United States, showed data from Sensor Tower but it is a very popular platform in China for services as varied as games and payment. It is also used to communicate with individuals and businesses outside China.

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AmCham Shanghai noted that over a third of respondents said the WeChat ban could lead to a loss of global revenue, with nearly 5 percent saying the hit could exceed 5 percent. Over 70 percent of respondents, however, said there would be little or no revenue impact should the executive order be limited to transactions within the United States, AmCham said.

Of the respondents, 88 percent said they used WeChat primarily as a communication tool with employees while 78 percent use it for marketing. Over 36 percent have partnership and content relationships with WeChat parent Tencent, the survey showed.

Trump's threat to ban WeChat has already upset millions of users in America who use the very popular app as an essential tool to keep in touch with family and friends in China. 

The ban could also become a major headache for U.S. companies with businesses in China and that depend on the app to operate. 

A bigger issue is that WeChat (Weixin) may no longer support the U.S. firms' order and payment systems if they are not allowed to use the app - they can't accept money via the app, let alone leveraging the platform to win over more customers.

On August 12, Tencent said it did not believe the ban would apply to its domestic equivalent Weixin, which could limit its impact on the company. Tencent assured that it uses data "in strict accordance with applicable laws and regulations." 

(With input from agencies)