The move, which confirms a proposal made by the European Commission last year, could have repercussions for U.S. businesses and British clearing firms after Britain leaves the EU in March.

The text, if adopted in talks with EU lawmakers which will follow in the coming weeks, could concern LCH, a unit of the London Stock Exchange, which dominates clearing of euro-denominated interest rate swaps and after Brexit will be outside the EU. The move could strip London of a chunk of that business.

If, "as a measure of last resort and on the basis of a fully reasoned assessment", the European Securities and Markets Authority (ESMA) decided that a foreign clearing house is of systemic importance for the bloc's financial stability, it could force that firm "to establish itself in the EU in order to be able to operate," the EU document said.

Even when relocation is not necessary, the draft rules would increase EU supervision of foreign clearers with activities in the bloc, a move that has been openly criticised by the U.S. financial regulator.

Christopher Giancarlo, chair of the U.S. Commodity Futures Trading Commission (CFTC), warned of possible retaliatory measures if EU regulators insisted on close supervision of U.S.-based clearing houses.

Large U.S. clearers such as CME and ICE could be concerned by the new rules.

(Reporting by Francesco Guarascio, Editing by Gabriela Baczynska and Ed Osmond)