Taoiseach Leo Varadkar is travelling to Brussels today for a high-stakes European Council summit.
The talks are expected to be dominated by the migrant crisis and Europe's trade war with the US.
Brexit will also feature high on the agenda.
British Prime Minister Theresa May will update leaders on her plans this evening, with the EU's chief Brexit negotiator Michel Barnier to give an update on negotiations tomorrow.
Taoiseach Leo Varadkar has said he is 'very disappointed' by the lack of progress in the negotiations.
— Leo Varadkar (@campaignforleo) June 27, 2018
Fianna Fáil's Brexit spokeswoman Lisa Chambers says the EU can't rely on Britain seeing sense.
She argued: "The hardline Brexiteers are motivated by a romantic notion of Great Britain, back to the Empire... I think the economic stuff, for some Brexiteers, is secondary to that."
While the summit has been seen as a key milestone in the Brexit talks ahead of October's deadline for a deal, migration has become the more pressing concern amid political turmoil over the issue in Italy and Germany.
In a letter to EU leaders ahead of the summit, European Council President Donald Tusk admitted the 'stakes are very high'.
More people starting to believe only strong-handed, anti-European & anti-liberal authority can stop illegal migration.
If people believe that, they will also believe everything else they say.
Stakes are high. Time is short.
— Donald Tusk (@eucopresident) June 27, 2018
He said: "The people of Europe expect us - and they have done for a long time now - to show determination in our actions aimed at restoring their sense of security.
"People want this not because they have, all of a sudden, become xenophobic and want to put up walls against the rest of the world, but because it is the job of every political authority to enforce the law, to protect its territory and the border."