Several senior EU sources have suggested that a possible breakthrough on the issue of the border on the island of Ireland may be close this evening.

One senior source told RTÉ News there have been several phone calls between British Prime Minister Theresa May and Taoiseach Leo Varadkar.

However, a British government source has said "we're not there yet", following speculation in the wake of an announcement by European Council President Donald Tusk.

Earlier this evening, Mr Tusk announced he would be making a statement at 7.50am (6.50am Irish time) tomorrow morning.

A spokesman later qualified the announcement by saying that Mr Tusk was due to fly to Hungary, so would simply be making a statement on any overnight developments.

Meanwhile, a spokesperson for European Commission President Jean-Claude Juncker said that the European leader spoke with both Mrs May and Mr Varadkar in separate phone calls.

This evening an Irish Government spokesperson said: "Matters are being considered as part of ongoing discussions involving the Task Force, the Irish Government and the British government."

A DUP source told RTÉ News tonight that "solid work had been done with some more to do" in relation to the details of the prospective agreement between the British government and the EU.

It was also confirmed that so far no phonecall has taken place between the British Prime Minister, Theresa May and DUP leader, Arlene Foster.

This indicates that the exchange of material by a DUP team in London and British government officials on a proposed text is continuing. But so far there has been no sign-off on an agreed document.  

According to one senior EU source: "There is a lot of activity. There is a desire to reach agreement tonight or tomorrow morning."

Earlier, a spokesman for Mr Juncker said Mrs May had an effective deadline of Sunday night if she wants to return to Brussels to seal a deal and hope to have agreement on trade talks next Friday.

Mr Tusk's role in the delicate choreography of reaching an accord had been to wait until Mrs May strikes a deal on making "sufficient progress" on divorce terms with Mr Juncker's Brexit negotiator Michel Barnier.

Mr Tusk would then confirm that he is asking the other 27 EU national leaders to consider draft guidelines on trade negotiations for approval at the summit he will chair.

However, Mr Tusk has also warned that time is running out for him to secure the agreement of the other leaders to opening the trade talks on such a tight schedule after Mrs May and Mr Barnier reach agreement.

Failure, officials say, would push any deal back into the new year, unnerving already worried investors in Britain.

Talks between the DUP and the British government to secure a deal on the post-Brexit future of the region's border continued today, according to a DUP spokesman.

"We have been talking to the government over the last couple of days and that is continuing today," the DUP spokesman said, saying deputy party leader Nigel Dodds and party Chief Whip Jeffrey Donaldson were involved but that Ms Foster remained in Northern Ireland.

"Ultimately if there is an agreement she will go over," he said. "Flights can be booked reasonably quickly but there is not an expectation of her going today."

Mr Varadkar has said he is willing to consider any proposed changes to the text of the deal that would allow the Brexit talks to soon move to Phase 2.

However, Mr Varadkar said he has little room to manoeuvre on what was outlined last Monday, but he will look at any proposals with an open mind.

Tánaiste and Minister for Foreign Affairs Simon Coveney, speaking in the Dáil today, said that "the core issues that Ireland got agreement on at the start of the week are not changing".

Mr Coveney said the Taoiseach has outlined that these are "sensitive negotiations at a sensitive time'" and he was not going to make a statement that would stoke up what is already "a difficult relationship management excercise".

Former taoiseach Bertie Ahern said it is a pity that the border issue is not "all wrapped up" but added that he is not "overly surprised" given the number of people and parties involved in the talks.

Speaking on RTÉ's Today with Sean O'Rourke, Mr Ahern said that he believed the best idea would be for the British government to try move nearer to a customs union for Northern Ireland, Scotland, England and Wales.

Today, the UK's House of Commons' Brexit Committee visited Armagh to hear about the risks and opportunities of Brexit for Northern Ireland.