Germany's financial regulator is hosting more than 20 banks to set out guidelines for setting up shop in Frankfurt following Brexit.
Bafin has brought together 50 representatives from those lenders for a full-day workshop addressing growing interest in shifting operations to the city following Britain's divorce from the EU.
The invite-only event - held at Bafin's Frankfurt office - is understood to have drawn major US banks including Goldman Sachs, which recently played down reports that it could cut London staff by half to around 3,000 and organise transfers to New York and to a new subsidiary in Frankfurt.
Citigroup and Morgan Stanley were also set to attend, according to reports.
Citigroup, which employs around 9,000 UK staff, is looking to shift its broker-dealer business to the EU, but will make a decision over the coming months.
All three banks declined to comment.
Representatives from the European Central Bank and Bundesbank were also reportedly at the event. Neither confirmed their attendance.
Global lenders, including JP Morgan and HSBC, have said that parts of their businesses would be moved from the City in response to Brexit and Prime Minister Theresa May's decision to rule out single market membership.
It means UK-based banks are likely to lose passporting rights - which allow financial services to trade freely within the EU's single market - and raises the possibility that London will lose out to rival EU financial centres such as Amsterdam, Paris, Frankfurt and Dublin.
HSBC has said it is on course to move 1,000 jobs from its London office to France, while around 4,000 of JP Morgan's 16,000 UK staff could be shifted abroad.
Barclays is eyeing a number of EU cities as part of Brexit contingency plans, and could end up bulking up its Dublin offices as a result.
However, it is not clear whether London jobs would be moved, or if new staff would be hired.
The Prime Minister said she held "positive" talks with bank bosses and business chiefs after a trip to the World Economic Forum in Davos, Switzerland, earlier this month, insisting that her vision of a "global Britain" would keep posts in the UK.
However, Goldman Sachs chief executive Lloyd Blankfein reportedly "talked tough" in his meeting with Mrs May and said there was no reason why European financial centres would not emerge as "effective rivals" to London, according to the Financial Times, citing sources.
Earlier this month, Mr Blankfein said New York is already gaining from Brexit as the US bank pulls back on previous plans to shift operations to Britain.