Huawei executive Meng Wanzhou has accused Donald Trump of "poisoning" her chances of a fair trial, according to newly filed documents that outline her emerging strategy in fighting US fraud charges.

The Chinese telecom giant's chief financial officer was arrested on a US warrant in December 2018 during a stopover in Vancouver, and court arguments had thus far been focussed on the narrow question of whether a US extradition request was lawful.

But a Canadian judge ruled in May that extradition proceedings could go ahead against Meng -- the 48-year-old daughter of Huawei founder Ren Zhengfei and known within the company as its "Princess" -- and a new phase opens in coming weeks that pivots to the actual charges.

Here are the main arguments and other key facts in a case with broad implications for US-China-Canada ties:

A 2019 US indictment accuses Meng and Huawei, the world's largest telecoms equipment manufacturer, with conducting business in Iran in violation of US sanctions.

US prosecutors say Huawei did so through Skycom Tech, a Hong Kong-registered firm that the Justice Department alleges was a poorly disguised Huawei front company.

The US says Skycom employees had Huawei email addresses and badges, and that Skycom's leadership were Huawei employees, including Meng, who has admitted previously serving on its board.

Huawei also at one point owned a stake in Skycom but sold its shares to another company, which the US says also was controlled by Huawei.

The indictment says Meng fraudulently concealed all this from HSBC -- a major Huawei banking client for years -- and other banks, putting those financial institutions at risk of unknowingly violating Iran sanctions.

In 2013, Meng made a presentation to an HSBC executive after the British banking group, worried over potential Iran exposure, requested an explanation.

Meng said Skycom was merely a "business partner" in Iran and that Huawei's dealings there did not violate global standards or US law.

"These statements were all false," the US indictment says.

A 2019 US indictment accuses Meng Wanzhou and Huawei with conducting business in Iran in violation of US sanctions
A 2019 US indictment accuses Meng Wanzhou and Huawei with conducting business in Iran in violation of US sanctions AFP / Don MacKinnon

In new documents that become public this week, Meng's lawyers deny any deception.

The new defence filings say the case was "poisoned" by statements from US President Donald Trump that Meng's lawyers say amount to political meddling.

In particular, they cite Trump's statement in a media interview two weeks after Meng's arrest that he would "certainly intervene (in her case) if I thought it was necessary" to preserve difficult US-China trade talks.

Meng's team also points a finger at HSBC, which in 2012 was spared US charges for activities including laundering Mexican drug-cartel money and previous Iran sanctions violations.

HSBC instead was ordered to pay a $1.9 billion fine, take corrective steps, and avoid new violations.

The new defence filings say HSBC was well aware of Huawei-Skycom activities in Iran but claimed ignorance to dodge further US punishment.

The US in February filed additional charges accusing Meng, Huawei and several subsidiaries over an alleged "decades-long" scheme to steal technology from US companies.

Huawei offered staff bonuses for such theft and recruited employees at other companies for the same, the charges say.

Huawei rejects the accusations -- which are not part of the current Canadian court action -- as "unfounded".

Meng's case has added to severe strain in Sino-US ties and created an unprecedented rift between Canada and China.

Soon after Meng's arrest, China detained former Canadian diplomat Michael Kovrig and businessman Michael Spavor. Espionage charges were filed against them in June, soon after Meng's bid to dismiss the US extradition effort was defeated.

Critics accuse China of taking the two men hostage in retaliation over Meng.

Former Canadian lawmakers and diplomats urged Prime Minister Justin Trudeau in June to drop Meng's case to free the "two Michaels", but he refused.

Trump, meanwhile, has warned of a "complete decoupling" with China amid soaring tensions over Huawei, trade, Hong Kong's status and other disputes.