"We stand with the international community in calling for the People’s Republic of China (PRC) to release, immediately and unconditionally, Canadian citizens Michael Spavor and Michael Kovrig," US Secretary of State Antony Blinken said in a statement.

"We continue to condemn these arbitrary detentions as well as the sentence imposed against Mr. Spavor on August 10. Mr. Spavor and Mr. Kovrig have not received the minimal procedural protections during their more than two-and-a-half-year arbitrary detention, and we stand with more than 60 countries who endorsed the recent Declaration Against Arbitrary Detention in State-to-State Relations," Blinken said.

"In my discussions with PRC officials, I have raised several cases of both U.S. and Canadian citizens subject to arbitrary detentions and exit bans in China, and I strongly support the immediate and unconditional release of all those whom the People’s Republic of China has arbitrarily detained," he said.

He said the practice of arbitrarily detaining individuals to exercise leverage over foreign governments is completely unacceptable.

"People should never be used as bargaining chips," he said.

The US leader said: "The United States also remains deeply troubled by the lack of transparency surrounding these legal proceedings and joins Canada in calling for full consular access to Mr. Spavor and Mr. Kovrig, in accordance with the Vienna Convention on Consular Relations and the China-Canada Consular Agreement."

"We call upon PRC authorities to grant the requests of Canadian officials and other foreign diplomats to attend their proceedings," Blinken said.

Earlier in the day, Spavor, detained by China in late 2018, was sentenced to 11 years in prison by a Chinese court on espionage charges.

Kovrig, detained at the same time as Spavor, is awaiting a verdict following his trial, which ended in March.