The Minister for Foreign Affairs Simon Coveney has said that EU fishermen will not be "sold out" in order to secure a future relationship agreement with the UK.
Mr Coveney said that while a deal was very much possible, there would be no breakthrough at this week's summit of EU leaders in Brussels.
He also said that any agreement reached between both sides would not be ratified by the European Parliament unless the UK removed legislation which breaches the Northern Ireland Protocol.
Negotiations on a future relationship have entered the final critical weeks, with fisheries, the so-called level playing field, and how disputes will be settled, still the key outstanding issues.
Since no free trade agreement is possible without an agreement on what access EU fishing fleets will get to UK waters, and how shared stocks will be distributed, there has been some speculation that the EU would compromise on the fisheries issue in return for the UK moving on the issue of state aid and the level playing field.
Speaking on the margins of a meeting of EU foreign and Europe ministers in Luxembourg, Mr Coveney said: "We value fishermen, we value their contribution across the EU and certainly EU fishermen are not going to be sold out in an effort to get an agreement on a future relationship with the UK on trade."
He said that while there had been some progress on the level playing field area, there had been "little or no" movement on fisheries. Both sides, he said, had legitimate concerns on the issue.
EU leaders are meeting for a summit in Brussels this week and will take stock of the negotiations. The British Prime Minister Boris Johnson has said the summit will be an effective deadline for a deal to be reached.
However, Mr Coveney said: "I don't see that there will be any major breakthrough this week."
Mr Coveney had bilateral meetings with both the EU's chief negotiator Michel Barnier, who briefed ministers on the negotiations, and the European Commission's vice-president Maroš Šefcovic, who is the Commission's representative on the Joint Committee, which implements the Brexit Withdrawal Agreement.
He said that while progress on implementing the Northern Ireland Protocol had been made, in a way which worked for people living in Northern Ireland and the island as a whole, the future relationship could not be finalised until the UK removed clauses in the Internal Market Bill which, he said, threaten the Withdrawal Agreement.
"There was a very clear message that if we do manage to negotiate a deal on a future relationship agreement that involves many different areas, before that deal can be ratified or finalised, the domestic legislation that the UK has introduced, effectively threatening to break the Withdrawal Agreement and Northern Ireland Protocol, that that legislation will need to be removed," he said.
"I think a deal is very much still possible. But there's an awful lot of work to do for the two negotiating teams. But for the European Union, the perspective is that unity is strength and today we got very strong unity on all of the issues."