Senior EU officials have warned that Ireland's interests in the Brexit negotiations will be held up due to the political vacuum in Northern Ireland.

The warning comes as the EU’s chief negotiator Michel Barnier set out tough and detailed guidelines ahead of the beginning of the talks.

Launching the EU’s draft negotiating directives, Mr Barnier said he would "pay particular attention to Ireland" in the first phase of the negotiations.

The document also says that the rights of citizens in Northern Ireland - where people can claim Irish, and therefore EU citizenship - would have to be addressed.

However, senior EU sources have warned that negotiators on both sides will be unable to get into the detail of the Irish issues while there is no functioning government in Belfast.

"We will deal with these issues as quickly as possible, but there are sensitive issues in relation to Northern Ireland,"  according to one senior EU source.

"Given both sides will have to consult with their respective constituencies, it will have to begin at a time which allows for discussion of the issue.

"For example, in the midst of a general election, it is not the right time."

Negotiators will also be hindered by the fact that the most difficult issues, such as trade and the transit of goods across the border and through the UK to continental Europe, depend on what kind of future arrangement the UK has with the EU.

This, say officials, will not be clear for some time.

"On the issue of transit of goods," according to another senior official, "that is something where we will have to have a better understanding of what the future relationship will be with the UK, in terms of customs.

"The fact that the UK has stated that they want to leave the single market and also customs union has inevitably had an impact on the controls of goods, including goods in transit, and here we have committed to looking for imaginative and creative solutions to mitigating the impact.

"But we will not solve all the Ireland specific issues in the first phase [of the negotiations]," the source said.

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A third senior EU official confirmed that the elections and the lack of a functioning executive meant that the directives being launched today lacked detail on the Irish issues.

"There's an understanding that the situation in Ireland is in flux," said the source.

"Northern Ireland is key. For the final agreement, you need to have full buy-in from the EU as a whole, the Irish Government, the British government, and the Northern Irish leadership.

It's not going work unless you have all four fully on board. At the moment there is no Northern Irish leadership. That makes things more difficult.

Minister for Foreign Affairs Charlie Flanagan said that not having an executive in Northern Ireland is an issue, but he expects that a deal will be agreed when parties return for negotiations after the British election in June. 

Speaking on RTÉ's Drivetime, Mr Flanagan said he has been advocating on behalf of Northern Ireland from an all Ireland basis, but that a Stormont executive is needed.

He said: "We do need a functioning executive in Northern Ireland and we need to know the Northern Ireland priorities because it would potentially adversely affect Northern Ireland than any other part of the UK. We have until the 29th of June to hammer out a deal.

"I believe we can do so within that time and I want to acknowledge the progress that was made on the part of the parties during the period since the 2nd of March, albeit not resulting in an agreement." 

This morning, Mr Barnier that warned that the UK would have to submit to the European Court of Justice in situations where EU citizens living in the UK beyond Britain's withdrawal wanted their rights protected.

He also insisted that the UK would have to pay all the financial commitments it had entered into, and that those payments could continue beyond departure.

However, he would not be drawn on a Financial Times report that the overall bill could amount to €100 billion.

Today’s guidelines set out in more detail that those adopted by 27 member states on Saturday.

Mr Barnier has said he needs to wrap up the talks by October 2018 to get any Brexit deal through the European Parliament in time for Britain's scheduled departure from the EU on 29 March 2019.

EU's Barnier says 'no punishment' in Brexit financial demands

Mr Barnier denied that the bloc's financial demands from Britain for leaving were "punishment" but warned against the "illusion" that Brexit would be painless.

He urged the British government to start talks as soon as possible and said that "the clock is ticking".

Mr Barnier told a news conference:

There is no punishment, there is no Brexit bill, the financial settlement is only about settling the accounts.

He was speaking after the British government rejected a report that Brussels could seek €100bn from the UK as the price of meeting financial commitments from its four-decade membership.

Britain's Brexit Minister David Davis said the EU could not bar Mrs May from joining Brexit discussions at future EU heads of government meetings while the UK remained a member state.

According to reports, Brussels was plotting to limit Mrs May's Brexit discussions to direct meetings with Mr Barnier.

Such a move would run contrary to Mrs May's claim that she would be negotiating directly on the terms of Brexit with fellow European leaders.

Mr Davis said: "The decisions in this exercise at the end of the day are taken in Council - that's a gathering of all the leaders of the European Union - and, frankly, until the day we leave, we are full members of the Union, we have every right to attend every Council and we will exercise our right.

"Just as we are obeying the laws of the Union, exactly to the letter, we are also going to expect our rights."

"The idea that somehow one side of the negotiation can dictate how the other side runs a negotiation is laughable.

This is an exercise in trying to shape public opinion and trying to pressurise us - it won't work.

Government's Brexit plan lacks political vision and ambition - Fianna Fáil

Meanwhile, Fianna Fáil's Brexit spokesperson said reports that the UK could be facing a Brexit bill of up to €100bn, could place Ireland in a "difficult position" which would be "extremely damaging" to Irish jobs, Irish agriculture, tourism and retail sectors.

Speaking on RTÉ's Morning Ireland, Stephen Donnelly said "the danger is the UK government and Prime Minister May ends up in a corner from which it's very difficult to move".

He also said the Government's Brexit plan lacks political vision and ambition.

Mr Donnelly said the strategy, released yesterday, is a "good introduction to Brexit" but what we needed was a plan.

He said there should be a detailed, costed, timetabled plan to detail how the Government will interact with farmers, tourism and people working in the UK but instead the report talks about "response plans that will be developed in time".

Mr Donnelly said this was "not good enough".

He described the outcome of last Saturday's meeting of the EU council as a re-statement of existing agreements.

Mr Donnelly also told RTÉ News that reports the UK could be facing a bill of €100bn could place Ireland in a "difficult position."

The Wicklow TD said it could be "extremely damaging" to Irish jobs, as well as the agriculture, tourism and retail sectors.