In this Nov. 9, 2017, file photo, President Trump walks with Chinese President Xi Jinping during a welcome ceremony at the Great Hall of the people in Beijing. (Andy Wong/AP)

The family of an American businessman sentenced to 10 years imprisonment in China on spying charges is urging President Trump to raise his case with Chinese President Xi Jinping when the two leaders meet this week at the Group of 20 summit in Japan.

Harrison Li, the son of the New York-based aircraft parts exporter Kai Li, is calling on Trump to raise the case of his father — believed to be the only American citizen held in China on state security charges — during a meeting with Xi this week, when Trump is expected to seek the release of two Canadians similarly detained by China's opaque security apparatus.

The encounter between Trump and Xi in Osaka appears likely to be dominated by the two countries’ disagreements over trade and technology, but the fate of detained Chinese and Canadian citizens caught in the escalating disputes could also be on the table.

Harrison Li said his father, who immigrated from China in 1989 as a student, acknowledged in a letter from detention that he routinely contacted U.S. government agencies as part of his work. His father may have been referring to his filings for export licenses, Li speculated. He insisted that his father's imprisonment was a “giant mistake.”

“My father is an innocent U.S. citizen in the crosshairs of some broader geopolitical conflict,” Li said. “He’s being used as a negotiating chip, a pawn, like unfortunately many other foreign citizens have been.”

Canadian Prime Minister Justin Trudeau said last week that Trump promised to ask Xi to release Michael Kovrig and Michael Spavor, two Canadians held by China in apparent retaliation for Canada’s cooperation with U.S. authorities in their pursuit of Huawei executive Meng Wanzhou. Meng, chief financial officer at the Chinese firm caught in the center of the U.S.-China dispute, is in Vancouver awaiting extradition to the United States, where she is wanted to face fraud charges related to Huawei’s dealings with Iran.

Harrison Li said Trump should use his meeting with Xi to intervene on behalf of his father, whose ordeal has gone largely unnoticed for nearly three years while the State Department and Li's supporters worked quietly, but unsuccessfully, to secure his release.

Li said his father was unfairly accused and used by China as a “geopolitical pawn” to gain leverage against Washington. He likened the case to China seizing Kovrig and Spavor to pressure Ottawa.

“There’s no reason why Trump shouldn’t bring up the case of a U.S. citizen who has been held on similar grounds — and frankly for a much longer period of time,” Li told The Washington Post. “This is really a call for help, because this can only be resolved through intervention from high-level leaders.”

China’s Foreign Ministry did not respond to a fax seeking comment about Li’s case.

Li is believed to be the first American citizen held by China on state security charges since Sandy Phan Gillis, a Texas business executive who was arrested during a trip to China in March 2015 and released two years later. Chinese authorities at the time accused Phan Gillis of working with the FBI to capture Chinese spies in the United States.

U.S. law enforcement in recent years has stepped up its pursuit of alleged Chinese spies as industrial espionage became a focal point in American complaints about Chinese practices. In one of several cases that embarrassed China, the FBI and federal prosecutors unveiled in October a successful sting operation that netted a Chinese intelligence officer in Belgium. 

Li’s case appeared unusual because he was accused of handing over Chinese state secrets to the FBI, which conducts counterintelligence operations but does not normally gather overseas intelligence, said John Kamm, a veteran activist who has lobbied the Chinese government for Li’s release.

“The FBI has rounded up lots of Chinese citizens in the U.S., and one wonders if there is some kind of tit-for-tat,” Kamm said.

In 2014, China detained a Canadian missionary couple on spying charges shortly after Canada arrested a Chinese man, Su Bin, at the behest of the United States for his role in a scheme to steal U.S. defense technology. China released Kevin and Julia Garratt around the same time Su plead guilty in U.S. federal court and served a short sentence.

Congressional lawmakers have called on Trump to press Li’s case and demand more information about his judicial proceedings. As in many Chinese cases involving state security charges, those proceedings were shrouded in near-total secrecy.

Details about Li's case first leaked in the pro-Beijing press. Citing unnamed sources, a Communist Party-backed Hong Kong newspaper reported before Li's trial in 2017 that Chinese law enforcement had tracked him visiting defense research institutes in Shanghai and Tianjin. Li would face severe punishment, the report predicted.

Following a six-month detention at an undisclosed location and without access to a lawyer, Li was convicted in August 2017 in an hour-long, secret trial that turned on allegations that he obtained Chinese state secrets — information that was, in fact, available online, his family and supporters argue.

Citing the case's sensitivity, China denied American diplomats permission to attend Li's trial and appeal hearing and only allowed them to observe his sentencing in January, a State Department official said. Diplomats have regularly visited Li in detention, most recently on May 7, the official said.

Senate Minority Leader Charles E. Schumer (D-N.Y.) told The Post this week that “the Trump administration must use all tools available to prioritize bringing Mr. Li back home so he can be reunited with his family in New York.”

The State Department in January renewed a travel advisory for China, warning American citizens that they could run the risk of arbitrary detention.

China’s Ministry of Culture and Tourism shot back a day later, warning Chinese travelers that they might face gun violence and police harassment in the United States.