Huawei chief financial officer Meng Wanzhou was arrested on December 1 while changing planes in Vancouver at the request of the United States, which says she committed fraud by lying to bankers about allegedly violating American sanctions on Iran.

She has been released on bail, but her arrest has sparked an escalating diplomatic crisis between Ottawa and Beijing.

Speaking to Chinese-language media in Markham, Ontario on Tuesday, after briefing lawmakers on the plight of two Canadians detained in China and a third placed on death row in what are widely seen as retaliatory moves by Beijing, Ambassador John McCallum said the US extradition request is seriously flawed.

"I think Ms. Meng has quite a strong case," he told a news conference.

"One, political involvement by comments from Donald Trump in her case. Two, there's an extraterritorial aspect to her case, and three, there's the issue of Iran sanctions which are involved in her case, and Canada does not sign on to these Iran sanctions. So I think she has some strong arguments that she can make before a judge," he said.

"And then the judge will decide whether he or she thinks (Meng) should be extradited or not."

Trump last month mused in an interview with Reuters about intervening in Meng's case if it would help him strike a trade deal with China.

Prime Minister Justin Trudeau, asked about McCallum's remarks on Wednesday, stuck to the government's position of non-interference in judicial matters.

"We will make sure that the rule of law is properly and fully followed," he said. "That, or course, includes the opportunity for (Meng) to mount a strong defense."

The opposition Tories, however, accused McCallum of possible "political interference" in the case and of discrediting the extradition process.

Meng's extradition hearing is expected to start in February. The process could take months or years.