The family of Canadian businessman Michael Spavor and former diplomat Michael Kovrig's bosses on Thursday called on China to release both men facing trial within days.
In the meantime, Canada's foreign ministry said Beijing had not yet granted Canadian officials permission to attend their trials.
"Despite several official requests to Chinese authorities, Canadian officials have not yet received permission to attend the trials," the department said.
In a rare statement cited by public broadcaster CBC, Spavor's family said they felt it "necessary to speak out and call for his unconditional release," adding that he was innocent of the accusations against him.
"His continued unjust detention depriving him of his liberty is both unfair and unreasonable, especially given the lack of transparency in the case," they said.
Richard Atwood, the president of Crisis Group, where Kovrig worked as a senior advisor, also said in a statement, "After 830 days imprisoned, Michael should be released immediately so he can return home to his loved ones."
The two Canadians were detained in December 2018 in apparent retaliation for Canada's arrest on a US extradition warrant of Huawei executive Meng Wanzhou -- roiling relations between Canada and China.
They were formally charged last June with spying, which Prime Minister Justin Trudeau has said were "trumped up."
Spavor and Kovrig are scheduled to go on trial Friday and Monday respectively.
Atwood said he was "disappointed" by Kovrig's pending prosecution, which coincides with a high-level meeting between US and Chinese top foreign officials in Alaska, saying: "From the moment he was detained, the political nature of his case has been clear."
"What happens in the Chinese legal system does not change this," he said, while the company's vice president Comfort Ero stressed that Kovrig's work in China was always "in the open and well known to Chinese authorities."
Spavor's family, meanwhile, described him as "just an ordinary Canadian businessman who has done extraordinary things to build constructive ties between Canada, China and the Democratic People's Republic of Korea."
"He loved living and working in China and would never have done anything to offend the interests of China or the Chinese people."