France said it would defend the interests of its biggest bank BNP Paribas, calling a possible $10 billion-plus U.S. fine “unreasonable” and warning it could have a bearing on transatlantic free trade talks. French government ministers have until now shied away from discussing in public BNP’ negotiations with U.S. authorities, who are investigating whether the lender evaded U.S. sanctions relating primarily to Sudan, Iran and Syria between 2002 and 2009.