Prime Minister Justin Trudeau reached out to Donald Trump on the day the United States opened new trade talks with China, urging him to maintain international pressure on Beijing to release two imprisoned Canadians and to leave the U.S. extradition request of a top Chinese telecom executive to the courts.

Mr. Trudeau telephoned the U.S. President on Monday to personally convey the importance of the rule of law as American and Chinese negotiators held their first face-to-face trade talks since the two countries agreed on Dec. 1 to a 90-day truce in their trade war.

In their discussions, Mr. Trump appeared to back off an earlier suggestion that he might use the extradition request of Huawei chief financial officer Meng Wanzhou from Canada to bargain for Chinese concessions on trade.

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According to the Prime Minister’s Office, Mr. Trump agreed that the Meng extradition process should be handled by the courts. U.S. law-enforcement officials reportedly allege Ms. Meng tried to bypass American sanctions on Iran and lied to U.S. banks about her actions.

“The two leaders discussed an extradition request made of Canada by the United States. They reaffirmed the importance of respecting judicial independence and the rule of law,” Mr. Trudeau’s office said in a brief summary of the discussions.

China had seized on Mr. Trump’s comments made in mid-December to claim that he was using Ms. Meng as a pawn in contentious trade talks and demanding Canada allow the Huawei executive to return home.

The Trump administration later vowed to ensure the Meng case would remain apolitical after Foreign Affairs Minister Chrystia Freeland went to Washington to protest Mr. Trump’s musings.

On Monday’s phone call, Mr. Trump said he was firmly committed to pushing Beijing to free former Canadian diplomat Michael Kovrig and entrepreneur Michael Spavor. Britain, Germany, France, the European Union and Australia have also called for the immediate release of the Canadians.

“The Prime Minister thanked the President for the strong statements of support by the United States in response to the arbitrary detention of two Canadians in China. The two leaders agreed to continue to seek their release," Mr. Trudeau’s office said.

The phone call between the two leaders came hours after a delegation of Canadian parliamentarians pressed Chinese officials to immediately release the two jailed Canadians, warning the continued detentions have caused a “major chill” in relations between both countries.

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Conservative MP Michael Cooper, one of the five lawmakers visiting China, said the delegation protested the treatment of the two men, who were arrested on Dec. 10 – nine days after Canada detained Ms. Meng, sparking angry protests from Beijing and threats of reprisals.

Ms. Meng was later granted bail and is now awaiting court proceedings while the two Canadians remain in jail and stand accused of engaging in activities that endanger China’s national security.

“We made it clear that from the standpoint of advancing important bilateral relations between Canada and China, that this represents a major chill,” Mr. Cooper said in a telephone interview from Shanghai. “Frankly, it is completely unacceptable that they are more or less denied access to consular services, they have been denied access to a lawyer, the detention conditions in which they are under are completely unacceptable. All of those points were raised.”

Mr. Kovrig’s employer, the International Crisis Group (ICG), says it has not heard anything directly from him since he was detained and does not know where he is being held. Canada’s ambassador to China, John McCallum, met with Mr. Kovrig on Dec. 14 but the detainee has not been visited by Canadian officials since. The ICG said it expects another consular visit to happen soon.

Karim Lebhour, a spokesperson for the ICG, said he believes Mr. Kovrig is likely facing the same treatment Canadians Julia and Kevin Garratt did when they were detained in China in 2014. Mr. Garratt spent 750 days in Chinese detention and was sentenced to eight years in prison for espionage before being deported. Ms. Garratt was detained for six months.

“We are not in a position to share any specific information about the conditions of his detention, but others in similar situations, like the Garratts, have described their condition of detention after having been released. They speak of intensive questioning several times a day, the lights in their room never switched off,” Mr. Lebhour said. “There is no reason to believe that it is otherwise for Michael.”

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Mr. Cooper said the delegation, which includes Senator Joseph Day and Liberal MPs Geng Tan, Majid Jowhari and Chandra Arya, met with Zhang Daogen, president of the Shanghai Academy of Social Sciences, and Sha Hailin, deputy-director general of the Shanghai People’s Congress. The MPs and senators belong to the Canada-China Legislative Association, which is funded by Parliament to promote relations between the countries.

The Chinese officials raised the issue of Ms. Meng and told the delegation that she has not broken any Canadian laws and therefore should be free to leave Canada.

“They said there wasn’t a basis upon which Canada could detain her,” Mr. Cooper said.

Canada and the United States have signed a treaty that requires both countries to honour extradition requests, although they have to be approved by the courts before a person is extradited.

Mr. Cooper said the delegation repeatedly stressed that there was no political involvement in the detention of Ms. Meng, who is out on $10-million bail. Canada’s courts are independent and the government cannot interfere, the Chinese officials were told.

He acknowledged the Chinese officials with whom they met are not high-ranking and would not have any influence over the detention of the two Canadians, but he said he was confident they would report their discussions to more senior officials.

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Mr. Cooper said members of the delegation will have other opportunities to directly raise the issue of the Canadians with Chinese officials, particularly when they travel to an Asia-Pacific parliamentary forum in Cambodia next week that will be attended by legislators from China’s National People’s Congress.

The visit to China by the parliamentary delegation had been planned well before Canada-China relations soured after the arrest of Ms. Meng.