British Prime Minister Theresa May's chief negotiator Olly Robbins has arrived in Brussels to seek a possible declaration that will clarify the nature of the Irish backstop in the Withdrawal Agreement, RTÉ News understands.
It is understood Mr Robbins is in discussion with EU chief negotiator Michel Barnier's deputy Sabine Weyand.
According to one senior EU source: "Robbins and the Task Force are in constant touch to see what they can do."
It is understood the UK will push for some kind of declaration before this week's summit of EU leaders.
During her statement to the House of Commons, Mr May said she would personally push for some shift on the backstop, although she did not spell out what that might be.
"In advance of the European Council I will go to see my counterparts in other member states, and the leadership of the Council and Commission, and I will discuss with them the clear concerns that this house has expressed," she told MPs.
One EU source was highly sceptical that Mrs May would succeed, saying: "I think it's impossible to sell this deal at this stage. The gap is so wide in terms of the numbers."
It is understood the focus of the discussions between Mr Robbins and the Task Force will be on the legal form of any side declaration, and its content, with the UK wanting more legal weight to reinforce the notion that the backstop will never be needed.
According to one EU source, a side declaration could expand on what the Political Declaration says about the Irish backstop.
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Paragraph 19 of the Political Declaration, which sets out aspirations for the future relationship between the EU and UK, already states: "The parties recall their determination to replace the backstop solution on Northern Ireland by a subsequent agreement that establishes alternative arrangements for ensuring the absence of a hard border on the island of Ireland on a permanent footing."
According to the source: "It's already crystal clear that, also from the EU side, there's no intention whatsoever to end up in the backstop.
"We really want to avoid that at all costs. If that needs to be spelled out another time, fine, it's already there."
Sources point to a declaration to secure the ratification in the Netherlands of the EU-Ukraine Association Agreement, which had been rejected by voters in a non-binding referendum.
In December 2016, EU leaders agreed a declaration spelling out that agreement did not guarantee EU membership to Ukraine, and that the Netherlands was not obliged to provide Ukraine with military assistance.
