Leaders of Scotland, Wales and Northern Ireland are meeting in Cardiff to coordinate a fresh push for independence and the break-up of the United Kingdom.
Scottish First Minister John Swinney, Welsh First Minister Rhun ap Iowerth and Northern Ireland First Minister Michelle O’Neill are expected to sign a memorandum of understanding committing their parties to closer cooperation on constitutional change.
Sinn Féin president Mary Lou McDonald will also attend the summit.
The agreement is expected to cover the economy, energy, relations with Europe, international cooperation and the right of the three nations to determine their own constitutional futures.
Swinney said the fact that Scotland, Wales and Northern Ireland are now led by pro-independence first ministers showed that the status quo was no longer sustainable.
He said Westminster must prepare for a future beyond the United Kingdom, arguing that independence would provide a fresh start for the nations.
The meeting comes after Prime Minister Andy Burnham indicated that another Scottish independence referendum could be held if there was a clear public consensus in favour of one.
However, Burnham has insisted that independence and another referendum remain off limits before the next general election, saying there is currently no clear consensus for separation.
In Northern Ireland, Sinn Féin is pushing for preparations towards a possible referendum on Irish reunification under the provisions of the Good Friday Agreement.
The party maintains that Irish unity is no longer a distant aspiration and that preparations should begin for a democratic vote on the issue.
The summit also follows comments by US President Donald Trump, who said during a visit to Dublin that he would like to see a united Ireland.
Under the proposed agreement, Scotland and Wales would seek closer ties with Europe and potential European Union membership if they become independent, while Northern Ireland would join the Republic of Ireland if reunification is approved.
The Cardiff summit marks a coordinated effort by nationalist leaders to increase pressure on Westminster and reshape the constitutional future of the United Kingdom.
