UBS has told members of its former private banking team responsible for rich US clients not to travel to America.
The Swiss bank has also made lawyers available to the more than 50 bankers involved, many of whom have left UBS since it decided last November to wind down its cross-border private banking business for US customers.
The move follows the recent indictment of one of the unit's former senior executives, Bradley Birkenfeld, who US authorities have accused of helping a billionaire client evade taxes. Mr Birkenfeld has pleaded not guilty and his lawyers have made no public statement on the matter.
Lawyers for Mr Birkenfeld and the US government are due to appear before a judge next Monday "to resolve pre-trial motions and discovery problems", according to court documents.