The trio of Wales and Northern Ireland and Scotland are planning to leave the United Kingdom and will sign a joint declaration to demand self-determination on Monday.

The Telegraph on Sunday reported that leaders of the three countries would meet in Cardiff, Wales’ capital, to discuss the possibility of exiting the UK. 

Four nations, including England, Scotland, Wales, and Northern Ireland, make up the United Kingdom. In 1707, England and Scotland formally came together to form Great Britain.

However, Ireland joined the union in 1801. While a large part of Ireland became independent in 1922, Northern Ireland remained part of the UK.

The planned meeting came amid heightened debates over Scottish independence and Irish reunification.

The MOU, designed to kick-start the process, is expected to be signed by Scotland’s First Minister John Swinney, Wales’ First Minister Rhun ap Iowerth, and Northern Ireland’s First Minister Michelle O’Neill.

The countries’ plan to leave the UK came a day after U.S. President Donald Trump, said he would love to see a united Ireland during his visit to Dublin on Saturday.

Mr Trump explained that it would be great to see Northern Ireland join the Republic.

The UK Prime Minister Andy Burnham, on Wednesday, said he would authorise another Scottish referendum if there was clear consensus for one.

The Monday’s meeting is expected to deepen pressure on Mr Burnham to authorise the referendum.

With John Swinney of the SNP in Scotland, Rhun ap Iorwerth of Plaid Cymru in Wales and Michelle O’Neill of Sinn Féin in Northern Ireland, the three devolved nations are for the first time making pro-independence move.

Meanwhile, Mr Swinney on Sunday described the status quo as unsustainable, insisting that the momentum behind serious constitutional change was undeniable.

“For the first time, Scotland, Wales and Northern Ireland are led by pro-independence first ministers. There could be no clearer sign that the status quo is not sustainable–and that Westminster must prepare for a post-UK future.

“Andy Burnham must now be facing up to the idea that he will go down in history as the final prime minister of the United Kingdom. Tomorrow in Cardiff, I am looking forward to discussing a better future with partners from across these islands–and that only comes with the fresh start of independence,” he stated.

After the meeting, the first ministers are expected to hold a press conference with their agreement covering four areas, including economy, energy, Europe and international cooperation and self-determination.