CNN Business  — 

For Zhang Lianping, a 72-year-old retired small business owner in College Park, Maryland, WeChat is a lifeline for staying in touch with relatives, old classmates and friends spread across Beijing, Shandong and Liaoning provinces in China.

“If we don’t have WeChat, we’re really going backward 40 years,” she said, in comments translated from Mandarin Chinese.

Tencent (TCEHY)’s popular messaging app could be banned in the US if the company doesn’t agree to sell it, as required by an executive order issued in early August. The Commerce Department said on Friday that as of Sunday the app would be prohibited from app stores. However, a federal judge on Sunday temporarily blocked the order, and the app will remain available for now.

WeChat is the latest target in President Trump’s rapidly escalating tech war with China, which has also put short-form video app TikTok under fire. The news has shaken Chinese Americans and anyone with ties to China who rely on the app as the main way of keeping in touch with family and friends there.

WeChat, called Weixin in China, functions like Facebook (FB), LinkedIn, Uber (UBER), Instagram and several other apps all rolled into one. For many Chinese people, WeChat is an indispensable app for connecting with the world.

“Everybody in China uses WeChat. It’s hard to appreciate how important it is for reaching people in China,” said Willy Shih, a professor at Harvard Business School focused on technology and management. “It appears like [the US] is trying to drop an Iron Curtain between the countries so that people can’t communicate with each other.”

The app is common especially among older generations of immigrants who left China many decades ago but still want to stay connected. And during the pandemic, when traveling back to China is complicated, expensive and involves an extra period in quarantine, many are staying put, making WeChat even more essential.

“I still want WeChat. It’s cheaper. Phone calls [to China] are expensive,” Zhang said.

Zhang Lianping, 72, retired small business owner in College Park, Maryland.

Zhang immigrated to the US in 1989 and began using WeChat over the past few years. Without WeChat, she envisions having to mail photos since she doesn’t know how to use a computer, and making phone calls to family and friends abroad. But with the large time difference between the East Coast and China, leaving messages on WeChat has been much more convenient, she said.

In the decades since she’s left China, her friends and family there keep her posted by sending photos of new skyscrapers emerging from old roads, vacations and the births of grandchildren. When her daughter delivers a baby in October, Zhang plans to send photos using WeChat to her siblings and old classmates. Without it, she said, she’ll have to use snail mail.

Ken Xiao, 63, who is retired but works as a calligraphy teacher in San Diego, said the Chinese community has heard rumors of a WeChat ban in the US for weeks and had discussed it on … WeChat.

Xiao immigrated to the US from Yunnan Province in 1989 and started using WeChat about four years ago. He now calls his parents every Monday evening using the app.

“I am really disappointed to hear this executive order,” he said.

Trump wrote in his executive order, “Like TikTok, WeChat automatically captures vast swaths of information from its users. This data collection threatens to allow the Chinese Communist Party access to Americans’ personal and proprietary information.”

He continued, “The United States must take aggressive action against the owner of WeChat to protect our national security.”

A Tencent spokesperson said the company is “reviewing the executive order to get a full understanding.”

Xiao and other Chinese Americans CNN Business spoke with conceded that they didn’t know whether the Chinese government could read their messages. They said they exercise caution when communicating with contacts, making sure not to delve too deeply into politics.

“As regular people, most of us Chinese people, including me and my students, we do not talk about anything related to the sensitive, political topics,” he said. “We can use [WeChat] as a regular life communication platform, so we don’t worry about anything else.”

If WeChat were to be banned in the US, Harvard’s Shih said Americans would likely have to resort to email to reach people in China, a mode of communication that isn’t as widely used in the country.

“If I send an email, I might not get a response for weeks, or the likelihood is I’ll never get a response,” Shih said.

Emily Kuo, 56, business owner in San Diego, California.

For Emily Kuo, 56, a business owner in San Diego, who immigrated from Guangdong Province in 1982, WeChat is a way to communicate with her tenants in her retail shopping center in California and talk to family and friends in China, including her son in Shanghai.

“You can leave long messages, very detailed messages. You can post, let’s say like a worksheet or a traveling itinerary. It’s very powerful. It’s really a very good communication tool,” Kuo explained.

“To me [the ban] is super inconvenient socially, but I think to many, many Americans who do business with Chinese in China, it would be a great interruption. It would be very inefficient,” she added. “I feel so sorry for them and for myself.”