By Liza Lin

A Shanghai company has filed a patent-infringement lawsuit against Apple Inc. that, if successful, could prevent the American tech giant from selling many of its products in its most important market outside the U.S.

Shanghai Zhizhen Network Technology Co. said Monday that it is suing Apple for an estimated 10 billion yuan ($1.43 billion) in damages in a Shanghai court, after a court decision in June that upheld the validity of its Chinese patent for a chatbot similar to Apple's Siri. Shanghai Zhizhen alleged the iPhone and iPad maker's products violated the patent the Chinese artificial-intelligence company owns for a virtual assistant whose technical architecture is similar to Siri's.

Siri, a voice-activated function in Apple's smartphones and laptops, enables users to dictate text messages or set alarms on their devices.

As part of the suit, Shanghai Zhizhen, also known as Xiao-i, asked Apple to stop sales, production and the use of products flouting the patent -- a category that includes virtually all the U.S. company's devices.

Apple said it was disappointed Xiao-i filed the lawsuit, adding that Siri doesn't contain features included in the Chinese company's patent, which relates to games and instant messaging.

"We look forward to presenting the facts to the court and we will continue to focus on delivering the best products and services in the world to our customers," Apple said in a statement.

China's Supreme Court ruled in late June that Shanghai Zhizhen's patent for the virtual assistant in China was valid. The decision ended an eight-year-long legal battle between the two companies in Chinese courts. Siri was introduced as an iPhone feature in 2011, and Shanghai Zhizhen sued Apple the following year.

If Shanghai Zhizhen applies for a preliminary injunction, the court could decide to bar Apple from selling products loaded with Siri in China for the duration of the trial, said Fang Jianwei, a former Chinese judge who is now a litigation partner at Zhong Lun Law Firm in Shanghai.

However, Mr. Fang said such injunctions have to meet strict conditions and are rarely granted by Chinese courts. And the patent-infringement suit isn't a surefire win for Shanghai Zhizhen, he added. While the Supreme Court ruled that the Chinese company's patent is valid, the current court could still find that the underlying technology behind Siri and Shanghai Zhizhen's patent is different enough to rule in favor of Apple.

China is second only to Apple's home market in terms of sales for the American brand. Apple boasts considerable cachet in China but has recently faced more competition from domestic device makers including Huawei Technologies Co., which surpassed Apple to become the world's top seller of smartphones in the second quarter of the year.

Apple said last week that its quarterly sales in China rose slightly to $9.33 billion, accounting for roughly 16% of its overall revenue for the three months ended June 27. Bolstering results were discounts on its iPhone 11 models and China's earlier recovery from the new coronavirus compared with the rest of the world.

Conflicts over intellectual property, technology and trade are driving bilateral relations between the U.S. and China to their lowest point in decades. Most recently, President Trump threatened to ban Chinese short-video app TikTok on national-security grounds. U.S. officials have been involved in talks over a potential sale of TikTok's American business to Microsoft Corp.

Apple has faced three lawsuits over intellectual property in China since 2012, when it agreed to pay $60 million to settle a trademark dispute with the mainland Chinese unit of another company, Proview International Holdings Ltd., which claimed ownership of the "iPad" name in China.

Apple lost another trademark battle four years later when a Beijing court ruled in favor of a Chinese company, Beijing Xintong Tiandi Technology Co., that made handbags, smartphone cases and other leather goods under the label "IPHONE."

Raffaele Huang contributed to this article.

Write to Liza Lin at Liza.Lin@wsj.com

Corrections & Amplifications China's Supreme Court upheld the validity of Shanghai Zhizhen Network's Chinese patent for a voice assistant similar to Apple's Siri in June. An earlier version of this article incorrectly said the company was awarded the patent in June. (Corrected on Aug. 3, 2020)