The European Commission will not formally adopt a draft text on the future relationship between the EU and UK on Wednesday as had been expected, RTÉ News understands.

Senior officials have played down the prospects of the EU's chief negotiator, Michel Barnier, bringing forward a text to be approved by the European Commission at its weekly meeting.

The lack of a formal text highlights the deepening caution and sensitivity over the Brexit negotiations, ahead of next week's critical summit of EU leaders in Brussels.

Over the next six weeks, both sides will have to conclude both the divorce treaty and a blueprint for the future relationship between the EU and UK once the two-year transition comes to an end on 31 December 2020.

It had been widely expected that the commission would adopt its version of that blueprint, known as the Joint Political Declaration, on Wednesday.

However, officials have stressed that Mr Barnier would be more likely to produce an "annotated" document, containing little more than headings, and even then that may not be formally adopted by the College of Commissioners on Wednesday.

It is understood that the key imperatives of concluding the Withdrawal Agreement and an accompanying Political Declaration are so grave, that trying to "digest" both at the same time may prove too taxing for a process that is already extremely sensitive.

The question of the Irish backstop remains the key obstacle in reaching concluding the Withdrawal Agreement, or divorce.

Yesterday, Tánaiste and Minister for Foreign Affairs Simon Coveney told Sky News that the Withdrawal Agreement was "90%" concluded.

A number of high-ranking sources in Brussels have, however, played down the optimism that was expressed over the weekend that a deal was imminent.

"This is quite a crucial week," said one senior diplomat.

"I'm a bit more cautious on this, because if I compare things to how the political dynamics were in the UK recently, and where we intend to land next week, there is still quite some work to do. I'm not saying it's not feasible."

While the Withdrawal Agreement and the Political Declaration are separate, they are inextricably linked.

Both Dublin and Brussels have insisted the backstop must be contained within a protocol embedded in the Withdrawal Treaty.

Observers have always seen the Political Declaration as providing important cover for British Prime Minister Theresa May. 

If it is detailed and spells out a close trade relationship, then it could make the backstop easier for Mrs May to sell to a sceptical Conservative Party and the DUP.

However, all the elements in play as we head to next week's summit are highly sensitive, as is the timing of any announcement on either the Withdrawal Agreement or the Political Declaration.

The fact that the UK has yet to table new proposals on the backstop has added to the sense of flux, with strong indications that London will not make issue a formal publication as such, instead preferring face to face talks in Brussels as to what might be politically feasible.

It is understood Mrs May's Europe adviser Olly Robbins is in Brussels for such discussions.

Brexit Secretary Dominic Raab is expected on Thursday.

"Everything is tentative at this stage," says another source close to the negotiations.

"Both sides agree there's no point in having set plans. It's not so much there's a rethink [on the commission's plans on Wednesday]. It's more a case suspending judgement.

"We have tentative plans, and the emphasis is on tentative. There are still big bits of the picture which are missing, namely what is going to come back from London [on the backstop]."

Another senior EU source was more emphatic that the commission would not produce a document on Wednesday.

A third source told RTÉ News: "Certainly if anything does come out it will be extremely telegraphic. It won't get into any substance. If they can get away without having to launch anything this week they will."

Much of the next ten days will hinge on what the UK proposes on the backstop.

All the indications are that London will call for the backstop to be UK-wide as far as customs are concerned.

Both the EU Task Force and member states have expressed significant reservations about this idea.

However, it will not be rejected out of hand before detailed proposals are put forward by London.

RTÉ News understands that at a meeting of EU ambassadors last Friday, the French ambassador said that Paris would keep an "open mind" but that France would not cross its red lines, that nothing in the UK proposals on the backstop should undermine the integrity of the Single Market, or limit the EU's autonomy on decision making.