BERLIN (AFP) - Germany's largest lender Deutsche Bank is bracing for Brexit and will have to move jobs from London to its headquarters in Frankfurt, chief executive John Cryan has said.

"For now, it's far from clear what Brexit constitutes, we are not really sure what shape it will take," Mr Cryan said in a video published on the bank's website Thursday.

"We will try to minimise disruption for clients and for our own people, but inevitably some roles will need to be either moved or at least added in Frankfurt," he said.

With some 9,000 employees in London - around one in 10 of its global workforce - Deutsche is the largest presence of any foreign bank in the UK.

Mr Cryan did not offer any idea of the number of jobs that might move to the German financial capital ahead of March 2019, when Britain will formally leave the European Union.

"But we will maintain a duplicated infrastructure at least for the transition period," he said. "We want to get to a position where London and Frankfurt can be used interchangeably."

In early July, Bloomberg News reported that Deutsche would move large parts of its trading and investment banking activities from London to Frankfurt over the coming 18 months.

Potential regulatory fallout from Brexit includes UK-based financial firms losing the right to do business with clients in the EU under so-called "passporting".

Frankfurt has so far led the field among continental European cities hoping to offer a haven to banks fleeing London.

Major US and Asian banks, including Goldman Sachs and Japan's Nomura, Daiwa and Sumitomo, have opted for the city on the Main river over European rivals like Amsterdam, Dublin and Paris.