Taoiseach Micheál Martin said the battle over a €1.85 trillion coronavirus recovery fund is a “prize worth negotiating for”.
Member states are deeply divided on how much of the fund should come by way of grants, and how much should be in the form of repayable loans.
As marathon negotiations continued, leaders appeared to be edging to a deal which would see €390bn in non-repayable grants being made available along with a similar amount in repayable loans for businesses.
Some countries wanted as much as €500bn in grants to be made available but this has been resisted by some northern nations.
EU leaders are in Brussels trying to agree the terms of the “unprecedented” recovery package. The summit began on Friday and had been scheduled to end on Saturday, but member states were divided, forcing talks to continue on Monday.
The negotiations pitted five wealthy northern states — the Netherlands, Austria, Denmark, Sweden and Finland — against southern nations hardest hit by the pandemic, supported by Germany and France.
Arriving for the fourth day of the EU summit, Mr Martin described it as “long and challenging”.
“The prize is worth negotiating for and the prize is for the opportunity for the entire European Union to work collectively to reboot and restart the European recovery, and to respond to the scale of the impact of Covid-19 on the economic, social and political life of the Union,” he said.
“This is unprecedented and the nature of the EU’s response that is being proposed is unprecedented, but it is necessary and it is the right response.
“Ireland is taking a constructive, activist role to ensure that a package of this scale is delivered which will enable member states, particularly member states who are under particular pressure from Covid-19, are in a position to respond to it and help their economies recover from it.
“We all benefit from the single market, we all benefit from the opportunities that the European Union opens up, and that is why, in my view, it’s extremely important that a strong message emanates from this summit, that Europe collectively can work together to deal with an unprecedented crisis in our history.”
EU Council President Charles Michel said he was convinced EU leaders would reach an agreement.
"We have worked very hard and this proposal is the fruits of lots of collective work with all the leaders and with their teams," Mr Michel told reporters.
"I know that the last steps are always the most difficult, but I am confident that even if it is difficult, it will be important to continue to work, and I am convinced that an agreement is possible."
Meanwhile, the vice president of the European Parliament is concerned at the "lack of mention" about the size of the next EU budget.
Fine Gael MEP Mairéad McGuinness told RTÉ's Drivetime that a strong recovery plan is needed in light of Covid-19 but so too is a strong budget for the next seven years.
"The fact that I haven't heard anything so far about the budget leaves me a little concerned about what might emerge", she said.