A lawyer for Huawei Chief Financial Officer Meng Wanzhou argued in a Vancouver court on Monday that she should not be sent to the United States for trial because her alleged crimes do not meet Canada's tests for extradition, in a case that has strained relations between Ottawa and Beijing.

Meng, 47, has said she is innocent and is fighting extradition in part because her alleged conduct was not illegal in Canada, an argument known as "double criminality."

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Unlike the US, Canada did not have sanctions against Iran at the time Canadian officials authorised starting the extradition process, her lawyers said.

The US has charged Meng with bank fraud and accused her of misleading HSBC Holdings Plc about Huawei Technologies Co Ltd's business in Iran.

Court proceedings show the US issued the arrest warrant, which Canada acted on in December 2018, because it believes Meng covered up attempts by Huawei-linked companies to sell equipment to Iran, breaking US sanctions against the country.

Meng, the daughter of Huawei's billionaire founder Ren Zhengfei, arrived in court for the first phase of a trial that will last at least four days, as China repeated its call for Canada to release her.

She remains free on bail in Canada and has been living in a mansion in Vancouver's exclusive Shaughnessy neighbourhood.

US case 'an artifice'

Extraditing Meng "would undermine the double criminality rule," Meng's lawyer Richard Peck told the court.

"Would we be here in the absence of US sanctions law, and ... our response is no," he said.

"In a typical case, double criminality is not contentious. This case, however, is founded on an allegation of breach of US sanctions, sanctions which Canada has expressly repudiated," he added.

Peck said the US cast the matter as a case of fraud against a bank, which he described as "an artifice".

"In reality, sanctions violation is the essence of the alleged misconduct ... the US has a global interest in enforcing its Iran sanctions. Sanctions drive this case," Peck added.

Meng's legal team is currently only scheduled to call evidence in the last week of April and a second phase of the trial focusing on abuse of process and whether Canadian officials followed the law when arresting Meng is set to begin in June. Closing arguments are expected in the last week of September and the first week of October.

Huawei, one of the world's biggest providers of telecommunications equipment, is at the centre of a significant dispute with the US.

The US Commerce Department in May placed Huawei Technologies Co Ltd on a trade blacklist, citing national security concerns. That allowed the US government to restrict sales of US-made goods to the company and a small number of items made abroad that contain US technology.

Huawei said in a statement that it stands with Meng in her pursuit of justice and freedom. "We trust in Canada's judicial system, which will prove Ms Meng's innocence," it added.

Legal experts have said it could be years before a final decision is reached in the case since Canada's justice system allows many decisions to be appealed.

Richard Kurland, a federal policy expert and lawyer in Canada who is not involved with the case, called Meng's double criminality argument around the absence of Canadian sanctions against Iran a sure bet.

"I think the defence has a slam dunk. There are no Iranian sanctions in Canada and anything (the prosecutors bring up) that's related to an Iranian sanction in Canada may well be dismissed," he said.

Politically motivated

Meng's legal team argued in November that she could not be extradited as Canada did not have sanctions against Iran at the time Canadian officials authorised commencing with the extradition, meaning her conduct was not illegal.

In response, Canada's attorney general said Meng was arrested on charges of fraud and misleading HSBC, which is a crime in both countries.

"Our government has been clear that we are a rule-of-law country and that we honour our extradition treaty commitments. That is what we need to do and that is what we will do," Canada's Deputy Prime Minister Chrystia Freeland said.

China has called Meng's arrest politically motivated. "The resolve of the Chinese government to protect Chinese citizens' proper legal rights is firm and unwavering," Foreign Ministry spokesman Geng Shuang told reporters during a daily briefing on Monday. He called Meng's case a "serious political matter."

Soon after her arrest in December 2018, China arrested two Canadians - former Canadian diplomat Michael Kovrig and businessman Michael Spavor. China has denied their arrests were related to Meng's case.

"The clear priority of everyone in our government ... is the release and wellbeing of Michael Kovrig and Michael Spavor. That is at the heart of all the work we are doing and rightly so," Freeland told reporters in Winnipeg on the sidelines of a cabinet retreat.

US President Donald Trump told Reuters in December 2018 he would intervene in Meng's case if it served US national security interests or helped close a trade deal with China. Freeland, who was Canada's foreign minister at the time, quickly warned Washington not to politicise extradition cases.