Britain is today expected to sign up to the Irish Border Brexit deal that it pulled out of on Monday.
British Prime Minister Theresa May is due in Brussels to finalise the negotiation.
A major breakthrough was signalled last night as a "tweaked text" aimed at getting the DUP to agree to a border deal was passed back and forth across the Irish Sea.
Sources in Dublin described the situation as "positive", but warned there was no complacency.
EU Commission President Jean-Claude Juncker discussed the situation with Taoiseach Leo Varadkar and Mrs May during separate phone calls.
"We are making progress, but not yet fully there. Talks are continuing throughout the night," said a spokesman for Mr Juncker.
Arrangements were being made for Mrs May to travel to Brussels early this morning for a joint press conference with Mr Juncker.
The talks stalled on Monday after the DUP learnt some details of the deal through the media, sparking a testy row with the UK government.
As renewed efforts neared a conclusion last night, all sides agreed to limit media comment until the deal was sealed.
The new text is thought to retain key elements demanded by the Government to protect the Good Friday Agreement and ensure "regulatory alignment" between Ireland and the North after Brexit.
Irish officials see the assurances as a "safety net" if the final deal results in a hard Brexit.
The extra text offers reassurance this will not undermine the North's place in the UK.