The UK will not accept a physical border on the island of Ireland, Taoiseach Leo Varadkar has said.
Mr Varadkar revealed that Theresa May made the British position clear in her address at the European Council summit dinner last night.
The Taoiseach said he was heartened by the Prime Minister's strengthened language on the issue.
"She specifically referenced the unique situation for both Ireland and Northern Ireland, which I think was very positive," he said.
"She strengthened her language in relation to the border.
"She said the UK would not accept a physical border on the island of Ireland - again, very positive language."
The Taoiseach said talks on the border question were "inching forward" but repeated his call for more detail.
"We don't have more detail yet - in a sense that's part of the difficulty," he said.
"We need to see sentiment backed up."
Brexit will dominate the second day of the summit, which involves all EU leaders bar Mrs May.
Mr Varadkar also said the question of the UK's divorce bill is not as big an issue for Ireland as it is for other countries.
He said his focus was on citizens' rights on the island of Ireland, Europeans living in Britain and British citizens in Ireland along with the question about of future UK-Ireland trade.
The Taoiseach also said EU leaders agreed that any changes to tax rules for digital multinationals should be done at a global level not at EU level.
And he said governments were keen to improve responses to natural disasters, with the wildfires that have raged across Portugal and Spain this year raised.
The impact of Storm Ophelia was also discussed at the summit, with the option left open for Ireland to apply for EU Solidarity funds over the next 12 weeks to meet the repair bill.