UK ministers have already suffered a heavy defeat over the rights of EU nationals living in the UK to remain post-Brexit.

"Otherwise I believe the peace process could unravel, as indeed Bertie Ahern, the former Taoiseach and so important to the success of that process has said."

Mr Pence did not mention the European Union in his speech.

Mr Davis said the British government was aiming for "a new, positive and constructive partnership between Britain and the European Union that works in our mutual interest".