Earlier, Britain published its negotiating mandate for trade talks with the United States, vowing to drive a hard bargain in negotiations that are set to test the two allies' "special relationship".

"Now the UK is free to negotiate outside the EU we will be aiming to begin negotiations with the U.S. as quickly as possible. The appetite is clear on both sides," Truss told parliament.

(Reporting by Elizabeth Piper, Writing by Kylie MacLellan)