The European Union and the United Kingdom have struck a new deal on the rules for post-Brexit trade in Northern Ireland

London (CNN) Britain and the European Union have reached an agreement on new trade rules northern IrelandTwo government sources told CNN, trying to resolve the thorny issue that has fueled post-Brexit tensions in Europe and on the island of Ireland.

European Commission President Ursula von der Leyen arrived in the UK on Monday for final talks with British Prime Minister Rishi Sunak, ahead of a statement on the deal in the House of Commons. And Buckingham Palace confirmed that von der Leyen will also meet King Charles III for tea at Windsor Castle.

Negotiations have intensified in recent weeks, after months of deadlock over how to handle border checks in Northern Ireland, which is part of the United Kingdom but shares a land border with the Republic of Ireland, an EU member state.

Now that the deal has closed, Sunak is facing a political backlash from Europe’s hardline hardliners in his conservative party.

Von der Leyen’s encounter with the king proved controversial. “The king is pleased to meet any world leader if he is visiting Britain and the government advises him to do so,” the palace said when announcing the sit-in.

According to a royal source, the meeting will be an opportunity for King Charles to discuss topics including the war in Ukraine and climate change.

But it was criticized by some prominent union figures. “I can’t quite believe Number 10 would ask His Majesty to be involved in finalizing such a controversial deal,” Arlene Foster, former Northern Ireland first minister, wrote in a tweet. . “It’s rude and it’s going to go down very badly in New Jersey.”

A new deal would update the arrangement known as the Northern Ireland Protocol, which was signed with Brussels by former Prime Minister Boris Johnson and which tried to acknowledge the delicate situation Brexit created in Northern Ireland.

A border between an EU member state and a non-EU country such as the UK usually requires infrastructure such as customs posts. But during a period of sectarian conflict known as the Troubles, security posts along the border between Northern Ireland and the Republic of Ireland became a target for paramilitary groups fighting for a united Ireland.

In theory, the Northern Ireland Protocol was intended to eliminate the need for border infrastructure. It was agreed that Northern Ireland would remain within EU regulatory scope, and that goods entering Northern Ireland from Great Britain would be screened before they arrived – effectively imposing a sea border.

This angered the pro-British Unionist community in Northern Ireland, who argued that they were cut off from the rest of the United Kingdom and forced closer to the Republic. Disputes over the arrangements have, in part, formed a barrier to restoring the Northern Ireland Assembly, which has been suspended since 2017. Power-sharing between Unionists and Republicans is a key part of the Good Friday Agreement – the peace deal that marked the end of the Troubles.

The disputes also affected trade between Great Britain and Northern Ireland to such an extent that the United Kingdom did not fully implement the Protocol.