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.”