US President Joe Biden will urge Prime Minister Liz Truss to work with the EU to resolve tensions around post-Brexit trading arrangements in Northern Ireland, the White House has said.
They will hold their first bilateral meeting on Wednesday, after Ms Truss travelled to New York for a UN summit.
Tensions between the two leaders have emerged over controversial UK plans to override the Northern Ireland Protocol.
Ms Truss has said she will not allow problems with the deal to "drift".
Speaking to reporters in New York, she said the UK must fix issues preventing the formation of a new government in Northern Ireland and ensure "free-flowing trade east to west as well as north to south".
Both Mr Biden and Ms Truss have said a negotiated resolution to the row over the protocol - which was signed when Boris Johnson was prime minister - between London and Brussels is preferable.
The basics
- The Northern Ireland Protocol is part of the Brexit deal: it means lorries don't face checkpoints when they go from Northern Ireland (in the UK) to the Irish Republic (in the EU)
- Instead, when goods arrive in Northern Ireland from the rest of the UK (England, Scotland and Wales), they are checked against EU rules
- The UK and the EU chose this arrangement because the Irish border is a sensitive issue due to Northern Ireland's troubled political history
The Northern Ireland Protocol is the post-Brexit agreement which allows for special trading arrangements between the Republic of Ireland and Northern Ireland.
It keeps Northern Ireland in the EU's single market for goods, avoiding the need for a hard border between the UK and Ireland after Brexit.
But it has been a source of tension since it came into force at the start of 2021.