Northern Ireland's First Minister Michelle O'Neill will meet with British Prime Minister Keir Starmer and Britain’s King Charles later at Windsor Castle.
Ms O'Neill will also be joined by Deputy First Minister Emma Little-Pengelly and other first ministers of the UK's devolved governments.
The gathering has been described as a "political engagement", which is being hosted by King Charles.
A Sinn Féin spokesperson said: "This is an opportunity to advocate for the best interests of people and communities on our island."
It is understood that while other leaders will stay the night at Windsor Castle, Ms O'Neill will not.
Scottish First Minister John Swinney and Welsh First Minister Eluned Morgan will also attend.
Ms O'Neill previously met King Charles when he visited Northern Ireland in 2022 after the death of his mother Queen Elizabeth II and she also attended his coronation the following year.
