US President Joe Biden will later tell PM Boris Johnson not to let the row over post-Brexit trading in Northern Ireland affect the peace process.
The two leaders will have their first face-to-face talks in Cornwall at 15:00 BST on the eve of the G7 summit.
Mr Biden will stress the need to "stand behind" the Northern Ireland protocol.
They will also discuss transatlantic travel and a new "Atlantic Charter" aimed at refreshing the relationship between the UK and US.