MONTREAL — Canada’s ambassador to China came under sharp criticism on Wednesday for appearing to politicize a high-profile legal case by saying publicly that the Huawei executive Meng Wanzhou had a good chance of avoiding extradition to the United States.
Speaking at a news conference for Chinese-language news media on Tuesday in Markham, Ontario, the ambassador, John McCallum, surprised seasoned observers of diplomatic protocol by offering an assessment of the case against Ms. Meng, who was arrested in December by Canadian authorities in Vancouver at the request of the United States.
Referring to comments that President Trump made this year that he was willing to intercede in the case if it would help secure a trade deal with China, Mr. McCallum said that Mr. Trump’s intervention, among other factors, had buttressed Ms. Meng’s case to avoid extradition.
“I think she has quite good arguments on her side,” Mr. McCallum said in remarks broadcast in the Canadian news media. He also cited “the issue of Iran sanctions which are involved in her case, and Canada does not sign on to these Iran sanctions.”
He added, “So I think she has some strong arguments that she can make before a judge.”
The remarks by Mr. McCallum, unusual for a senior diplomat in a sensitive case under the global spotlight, have complicated matters for the Canadian government, which has emphasized that it would not interfere politically in the case.
The arrest put Canada in the middle of a thorny legal battle between China, which says that Ms. Meng’s arrest was an abuse of law, and the Trump administration. The Americans are seeking to extradite Ms. Meng to stand trial on charges that she lied to American banks about Huawei’s efforts to evade Iran sanctions.
Canada has been concerned about three citizens held in China, including Michael Kovrig, a former diplomat, and Michael Spavor, a businessman, who have been detained on suspicion of “endangering national security.” The third Canadian, Robert Lloyd Schellenberg, 36, was sentenced to death this month in China for drug smuggling.
Asked on Wednesday whether he agreed with Mr. McCallum’s assessment, Prime Minister Justin Trudeau said that Canada was “a country of the rule of law.”
“We will make sure the rule of law is properly and fully followed,” Mr. Trudeau said during a news conference in La Loche, Saskatchewan. “That includes the opportunity for her to mount a strong defense. That is part of our justice system.”
Adam Austen, a spokesman for Foreign Minister Chrystia Freeland, said no political considerations have been applied in the case. “With respect to Meng Wanzhou, Huawei’s chief financial officer, Canada is conducting a fair, unbiased and transparent legal proceeding,” he said.
But the Conservative opposition leader Andrew Scheer criticized Mr. McCallum, a former minister of immigration in Mr. Trudeau’s Liberal Party government, saying that it was “completely unacceptable” for him to comment on a case pending in a Canadian court.
“John McCallum, as ambassador, has a very special place in this whole dynamic. He’s not someone with an opinion, or a professor opining,” Mr. Scheer told CBC News on Wednesday. “If I were prime minister I would fire John McCallum.”
The United States is expected in the coming days to formally request that Canada extradite Ms. Meng. It has until Jan. 30 to make the request. Once it is made, the Canadian courts will then decide whether she can be extradited, with a final determination made by the minister of justice.
The formal request would come at a sensitive moment: American and Chinese officials plan to meet in Washington next week for a critical round of negotiations to end a monthslong trade war.
Mr. McCallum is known to speak his mind. Last year, he observed that in key policy areas such as the environment, global warming, free trade and globalization, Canada’s policies were closer to those of China’s government than those of the United States under President Trump.