Chinese telecom giant Huawei is taking the bank HSBC to court in the UK as part of its attempt to prevent the extradition of its chief financial officer from Canada to the US.
Meng Wanzhou was arrested in Canada on a US request over claims she misled HSBC in a 2013 meeting, reports the BBC.
Huawei now hopes to gain access to HSBC documents that could help it undermine the US case for her extradition.
The move comes amid political pressure on HSBC, which is UK based but was founded in Hong Kong where it makes much of its profits.
The court hearing in London on Friday draws the bank deeper into a legal battle which has raised tensions between Canada and China.
Meng Wanzhou, who is the daughter of Huawei's founder, was arrested at Vancouver airport on 1 December 2018 because the US wants her to stand trial on charges including fraud. These are linked to the alleged violation of US sanctions against Iran, allegations she denies.
A meeting between Meng and HSBC on 22 August 2013 is central to the claims.Reuters news reports in the preceding months had raised questions about whether there had been a breach of trade sanctions on Iran by Hong Kong-based firm Skycom.
At issue was whether Skycom, a telecoms equipment seller, was simply a business partner of Huawei's - or a front for it to conceal its activities in Iran.
The US alleges that in the meeting Ms Meng misled HSBC over the true nature of Huawei's relationship with Skycom and this, in turn, put the bank at risk of violating sanctions against Iran. But it was more than five years after the meeting that she was detained.
Her Canadian lawyers have followed a multi-pronged strategy to try to prevent the extradition.