US President Joe Biden will tell PM Boris Johnson not to let the row over post-Brexit trading in Northern Ireland affect the peace process.
The two leaders are having their first face-to-face talks in Cornwall 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.
The US President is on his first overseas visit since being elected and the G7 summit is the first time world leaders have all gathered in person since the pandemic began.
The rollout of the coronavirus vaccination programme and climate change are high on their agenda.
But the ongoing dispute between the UK and the EU over regulatory checks on goods going into Northern Ireland from Great Britain is also likely to feature heavily in diplomatic discussions in the coming days.
President Biden has a close interest in Ireland, given his ancestral roots, and had warned that the Good Friday Agreement must not be jeopardized by rows over trade.
The US was closely involved in drawing up the agreement – with American senator George Mitchell chairing the talks which led to the peace deal.
Business and political leaders in Northern Ireland have warned that the trade dispute is causing political angst and instability in the run up to the marching season next month, a historical flash point between loyalist and nationalist communities.