As the vote in the UK draws closer, Wall Street is regarding the possibility that the British might quit the European Union next month as increasingly real.
Most of Wall Street is opposed to a Brexit, and more bank CEOs are speaking out about it.
At Morgan Stanley's annual meeting, CEO James Gorman took an opportunity in his speech to caution voters in the UK about the gravity of the decision they were preparing to undertake.
"We believe that leaving the union could be damaging to the UK economy and to the city," Gorman said at the bank's meeting in Purchase, New York on Tuesday.
Gorman declined to explain how the bank would respond to a Brexit scenario, but reminded reporters after the shareholder meeting that Morgan Stanley would have two years after the vote to make changes to comply with any new regulations.
"Every bank has to put together a contingency plan," he said after the meeting. "We're not taking any action yet."
Gorman's comments come as a number of prominent Britons have banded together and spoken out against a vote to leave the EU. But a Brexit would also likely prove damaging on Wall Street and elsewhere for banks.
Industry analysts and experts say that banks with a strong presence in the UK would have to relocate key offices, should the measure pass when it comes up for a vote June 23. Because the UK is a part of the EU, London is one of the key cities for bank regulators, as well as banks themselves.
Further, a Brexit could fuel rising cost of capital, which would make it tougher to do deals.
Wall Street executives have had to throw together plans for how to manage their way around a potential regulatory headache in the event that Britons ultimately decide to quit the governing collective.
Citigroup CEO Michael Corbat said some operations might be shuttled to new EU cities, including the bank's European trading business, when asked during the bank's April earnings call. how he might respond to a Brexit.