A deal preserving the Common Travel Area (CTA) between the UK and Ireland after Brexit is to be signed later.
The memorandum of understanding between the two governments allows citizens of both countries to cross the Irish border and move freely between Great Britain and the Republic of Ireland.
It allows cross-border access to education and healthcare.
The non-legally binding understanding will be signed by British and Irish ministers at a Cabinet Office meeting of the British-Irish Intergovernmental Conference in London on Wednesday.
It is part of a renewed bid to restore devolved powersharing at Stormont, launched after the murder of journalist Lyra McKee in Londonderry.
Working groups addressing contested issues like identity are due to begin operating on Wednesday.
The CTA predates the UK and Ireland’s membership of the EU.
There was no legally binding international agreement which established its terms and it was largely based on trust. The memo is an attempt to reinforce that understanding.
It is expected to be signed by UK Cabinet minister David Lidington and Irish deputy premier Simon Coveney, with Northern Ireland Secretary Karen Bradley in attendance.
The intergovernmental conference is provided for by the 1998 Good Friday Agreement and facilitates bilateral co-operation between Britain and Ireland.
It was resurrected after seldom being used because of the absence of a breakthrough at Stormont.
The fresh powersharing talks process began in Belfast on Tuesday.
Leaders of the five main parties acknowledged mounting public impatience and anger at a stalemate that has left the region without a functioning devolved government for over two years.
They held a short round-table meeting at Stormont House on Tuesday afternoon for the first exchanges of a new process initiated by the UK and Irish governments.
The process will involve agenda-setting and stock-taking meetings between the five leaders and two governments at least once a week, with five working groups to focus on the detail of key disputes at the heart of the deadlock.
The last DUP/Sinn Fein-led powersharing coalition imploded in January 2017 when the late Martin McGuinness quit as Sinn Fein deputy first minister amid a row about a botched green energy scheme.
The fallout over the Renewable Heat Incentive (RHI) was soon overtaken by disputes over the Irish language, the region’s ban on same-sex marriage and the toxic legacy of the Troubles.
Six previous initiatives to restore devolution failed to find consensus.