US President Joe Biden will bring a grave Brexit warning to his first meeting with British Prime Minister Boris Johnson: Prevent a row with the European Union from imperilling the delicate peace in Northern Ireland, write Steve Holland and Guy Faulconbridge.

In a move rarely seen between allies, Washington issued London with a demarche: a formal diplomatic reprimand usually reserved for adversaries.

The president of America will tell Boris Johnson not to let the row over Northern Ireland's Brexit arrangements put the Good Friday Agreement at risk as the two meet up in Cornwall ahead of G7 summit on Thursday.

Brussels ready to slap tariffs and quotas on UK exports – and even to ‘suspend cooperation in certain sectors’

Joe Biden's administration has warned the British government against anything that would put the Northern Ireland peace process at risk.