OTTAWA, Canada — Prime Minister Justin Trudeau on Monday blasted China's detention of two Canadians for "political ends," following charges against them for spying.

His comments came after China's Supreme People's Procuratorate on Friday said it had begun the prosecution of ex-diplomat Michael Kovrig and businessman Michael Spavor, who were "suspected of foreign espionage" and "providing state secrets."

The move, 18 months after their arrest in a spat between the two countries, came just weeks after a Canadian judge ruled that proceedings to extradite Chinese Huawei executive Meng Wanzhou to the United States will go ahead.

Relations between Canada and China have hit rock bottom over the arrests. 

At his daily briefing on Monday, Trudeau said: "This arbitrary detention of Canadian citizens is unacceptable and deeply concerning, not just to Canadians but to people around the world who see China using arbitrary detentions as a means to political ends." 

Trudeau said "we deplore... a political decision made by the Chinese government" which continues to pressure Canada.

Beijing has also blocked billions of dollars' worth of Canadian agricultural exports.

'Pawns in bigger geopolitical game'

Trudeau last week said he was "disappointed" that the Canadians were formally charged with spying, and his deputy, Chrystia Freeland, said she was "heartbroken and really angry" over Beijing's action.

Former ambassador to China, Guy Saint-Jacques, had urged Ottawa to take a more aggressive stance, "not just soft diplomatic talk anymore."

In an interview with public broadcaster CBC, Kovrig's wife Vina Nadjibulla agreed more pressure on China was needed, as "words are no longer enough."

But she said "I'm interested in us being strong, but not antagonistic. We cannot win a race to the bottom with China, we cannot become aggressive and confrontational because confrontation is not a strategy."

Nadjibulla insisted that both her husband and Spavor are innocent and "pawns in a bigger geopolitical game."

It is "heartbreaking," she said, knowing that Kovrig is languishing in a cell he described in letters to her and other family as a "concrete jungle."

"Basically he has been confined to a single cell this entire time. He has not gone outside. He has not seen a tree or had fresh air to breathe for 560 days," she said.

Allies 'extremely concerned'

Earlier Monday, US Secretary of State Mike Pompeo demanded that China free the two Canadians, and said in a statement that his country "rejects the use of these unjustified detentions to coerce Canada."

Australia, Britain, France, Germany, the EU and others have also pressed China over the detention of the Canadians.

Trudeau thanked allies for "speaking up" against Beijing's use of what observers have described as "hostage diplomacy."

"Our allies around the world," he said, "are extremely concerned about the plight of Canadians because they know very well that it may one day be their turn."

Kovrig and Spavor were detained in December 2018, nine days after Meng was arrested in Canada on a US warrant.

The United States wants to try her on fraud charges related to the Chinese telecom giant's alleged violations of US sanctions against Iran.

Meng, the eldest daughter of Huawei founder Ren Zhengfei, has been out on bail and living in a mansion in Vancouver, while the two Canadians remain in China's opaque penal system.

"It's a real shame that China continues to punish Canadians for a decision by our independent judicial system in Meng's case," Trudeau commented.

Former senior Canadian officials have proposed a prisoner swap of sorts, intervening in the extradition hearing to release Meng in exchange for the repatriation of the two Canadians.

Nadjibulla said she obtained a legal opinion that Canada's justice minister can step in at any time to quash Meng's extradition, but "whether the minister should act is a second question."

Trudeau responded to the idea bluntly: "No. We're not considering that."