Theresa May warned that although Brexit talks with the EU are "now in the endgame", there are still significant issues that separate London and Brussels.
With Britain's planned departure from a March exit from a multinational trading block, which is still on the horizon, questions remain about whether a withdrawal agreement can be concluded.
Here are answers to some of the main questions about what is still separating both sides:
– What is the biggest obstacle to the agreement to withdraw?
The main remaining issue is the border between Northern Ireland and the Republic, while the UK and EU parties are divided on the best way to avoid the need for control points – the so-called "Hard Borders".
– Why do they want to prevent heavy frontiers?
Regulatory and customs controls on hundreds of crossings that thousands of vehicles use on a daily basis could cause massive disruption to individuals and businesses.
The open border was also part of the Big Friday deal that ended the decade of violence, and there are fears that checkpoints and cameras could be the cause of sectarian attacks.
– What is the UK Government's preferred solution?
London believes that borders can remain open as part of a wider trade deal that eliminates the need for controls.
– What does Brussels propose?
The European Union insists that the "feedback" agreement be used as a back-up facility that will be used until a wider agreement is in place.
This would mean that Northern Ireland would indeed remain part of the European customs area, with inspections carried out in ports and ferries between the region and the British mainland instead of the border.
– What does the UK think about it?
Theresa May has repeatedly said that no Prime Minister can adopt such a plan because it would create a customs border for the Irish Sea and undermine the integrity of the United Kingdom.
– So what does London suggest?
Mrs. May has proposed alternative measures to allow the UK to be temporarily arranged in a customs union, which it expects to be lifted by the end of 2021. On Monday, she warned she would not accept "any agreement costs".
– Is it acceptable for Brussels?
Only if there is a "Feedback Feedback," so when a temporary agreement expires throughout the UK, Northern Irish will come into force.
– What does Ireland say about feedback?
Taoiseach Leo Varadkar said last week: "There can not be an expiration date, and there can be no unilateral termination clause, and if it were one of those things, feedback would not be worth the way it is written."
– Does Mrs May have at least support in the UK for her proposal?
Many conservatives – allegedly including some ministries – are concerned that "temporary" feedback becomes permanent and they want any agreement to contain a firm deadline for its abolition. Others on the Remain side fear that Britain would be the rule of no word on much of the economic policy.
– If Mrs May can agree with Brussels, can she get through Parliament?
This is very controversial. Depending on the nature of any business, it might lose support from 80 difficult Brexiteers lines on one side of their party or 30 Europhile tories on the other.
Ten MEPs have clearly stated that they will not support anything, which means that Northern Ireland is treated differently than the rest of the United Kingdom.
And the PM will try to earn a lot of support from Labor MPs, with the party leader insisting he will vote on anything that fails six tests.