The U.K. and U.S. sought to allay fears of disruption in themulti-trillion-dollar derivatives market, vowing to put in placeemergency policies to ensure trading continues uninterrupted in theevent of a no-deal Brexit.

The heads of the Bank of England (BOE), Financial ConductAuthority (FCA), and U.S. Commodity Futures Trading Commission(CFTC) promised a seamless transition after the U.K. leaves theEuropean Union (EU), whatever form the separation takes. Theagencies' moves would help traders use many key exchanges andclearinghouses, including those run by the London Stock ExchangeGroup Plc., CME Group Inc., and Intercontinental Exchange Inc.

The authorities said they would carry over existing agreementsstruck between the EU and the U.S. because those will no longercover the U.K.'s relationship with America post-Brexit. Without anarrangement in place, trillions of dollars in swaps, futures, andother derivatives could be thrown into question at the world'sbiggest banks and money managers.