Canadian Prime Minister Justin Trudeau called Thursday on the United States not to sign a trade deal with China unless Beijing agrees to release two Canadians detained since last year.

Former diplomat Michael Kovrig and businessman Michael Spavor have been held in China's opaque legal system since they were apprehended on December 10, 2018, accused of espionage.

Their case is widely viewed by Canadians as retribution for the arrest of Huawei chief financial officer Meng Wanzhou in Vancouver just nine days prior. She is wanted in the United States on charges related to Iran sanctions violations.

Obtaining the two men's release has been a top priority of Trudeau's government.

When asked if he thought a US-China trade deal could help resolve the situation during an interview with French-language channel TVA, Trudeau responded: "We hope so."

"We told them that the United States must not sign a final and complete deal with China that does not solve the problem of Meng Wanzhou and the two Canadians," he added.

Trudeau, who has been criticised by the opposition for his handling of the case, also said his administration has worked "practically every day to try and make China understand that they must free these two Canadians."

Meng was released on bail a few days after her arrest. She is living in her Vancouver mansion while waiting for an extradition hearing scheduled to begin January 20.

"Whatever pressure they put on us, arresting two Canadians... Won't change the Court of British Columbia's decision on extradition," Trudeau warned, noting that the Canadian judicial system is "independent."