European Commission vice president Maros Sefcovic has said discussions around the Northern Ireland Protocol will not be a renegotiation.
The EC has laid out measures to slash 80% of regulatory checks and dramatically cut customs processes on the movement of goods, especially food and farming produce, between Britain and the island of Ireland.
The Government welcomed the announcement, signalling it wants “intensive talks” to follow the EU’s proposals.
At the same time, however, a Government spokesman said there have to be “significant changes” to the Northern Ireland Protocol in the Brexit Withdrawal Agreement if there is to be a “durable settlement”.
Brexit minister Lord Frost is expected in Brussels on Friday to meet Mr Sefcovic to discuss ways to break the deadlock.
Mr Sefcovic spoke to Northern Ireland’s political leaders on Thursday.
Afterwards, he said he has no mandate to renegotiate the protocol.
“Now we should really do the last mile, work constructively with all the proposals we put on the table, put it finally to bed,” he told BBC Northern Ireland’s The View programme.
“I believe that we could be in the home stretch with our proposals on the table and as I said, let’s try to solve all these issues before Christmas because I think that would be the best Christmas gift we can give to the people of Northern Ireland.”
However, Mr Sefcovic added: “I have no mandate to renegotiate the protocol … the withdrawal agreement, protocol and trade and cooperation agreement, we signed it, we ratified it, it’s international law and I think we should respect it.”
Earlier, speaking on BBC2’s Newsnight, EU ambassador Joao Vale de Almeida said Brussels has gone the “extra mile” and cannot go any further following Wednesday’s proposals.
“We went to the limits of what we can do to address the problems of Northern Ireland because we care for Northern Ireland,” he said.
“These problems were caused by Brexit.”
He stressed that the EU cannot accede to a key British demand to remove the role of the European Court of Justice (ECJ) in overseeing the protocol.
“There is no single market without the European Court of Justice. It’s the referee of the single market,” he said.
Lord Frost has previously said the role of European judges is something the UK cannot accept.
But in a sign that he may be willing to compromise, he told peers on Wednesday that he never used the term “red lines” in his negotiations.
Under the terms of the protocol, which was agreed by the UK and EU as part of the 2020 Withdrawal Agreement, the ECJ would be the final arbitrator in any future trade dispute between the two parties on the operation of the protocol.
The UK now wants to remove that provision and replace it with an independent arbitration process.
One option reported to be under consideration by Brussels is a reduced role for European judges.
The Times reported that under the plan, disputes would go to an independent arbitration panel, with the ECJ asked to interpret narrow matters of EU law as a last resort after dispute resolution has failed.
Cabinet minister Sajid Javid said ending the role of the ECJ is one of the key points.
The Health Secretary told Sky: “Looking forward, there should not be a role for the European Court of Justice in any part of the UK and that includes Northern Ireland.
“I think it is an over-legalistic approach that the court has. Lord Frost has been really clear about this with the speech that he made this week. One of the most important issues is to end the role of the ECJ in Northern Ireland.”
The package of proposals already set out by the EU would remove the prospect of certain produce, including sausages, being banned from being shipped from Great Britain to Northern Ireland.
The EU plan also includes a 50% reduction in customs paperwork required to move products across the Irish Sea.
In return, the trading bloc has asked for safeguards to be implemented to provide extra assurances that products said to be destined for Northern Ireland do not end up crossing the Irish border.
Those include labelling certain products to make it clear they are for sale in the UK only, and enhanced monitoring of supply chain movements and access to real-time trade flow information.
The EU plan amounts to a set of counter-proposals in response to a wish list of protocol reforms outlined by the UK Government in July.
The proposals from both sides are now set to form the basis of a new round of negotiations between Brussels and London in the weeks ahead.
The Northern Ireland Protocol was agreed by the UK and EU as a way to sidestep the major obstacle in the Brexit divorce talks – the Irish land border.
It achieved that by shifting regulatory and customs checks and processes to the Irish Sea.
But the arrangements have created new economic barriers on goods moving from Great Britain to Northern Ireland.
This has caused disruption to many businesses in Northern Ireland and has also created a major political headache for the Government, as unionists and loyalists are furious at what they perceive as a weakening of the Union.
First Minister of Wales Mark Drakeford said he is “frankly baffled” by the UK Government’s stance, adding: “It is their deal, yet so often we hear UK Government ministers talk as though the deal was entirely somebody else’s responsibility.”
He told Sky News: “It’s a very important issue for Wales because our ports face the island of Ireland and trade through our ports is significantly down following Brexit.”