Leo Varadkar struck a conciliatory tone at the end of the Salzburg summit as the UK was put on notice that the EU is prepared for a no-deal Brexit if concessions are not made on the Irish question.
The issue of an Irish protocol - which would ensure a frictionless border on the island of Ireland no matter the outcome of Brexit - has remained a sticking point in reaching a deal.
European Council president Donald Tusk has said a meeting next month of the EU Council will be a "moment of truth", adding that "results will be expected".
The EU wants an agreement in principal that can be "finalised and formalised" in November.
British prime minister Ther-esa May told the Taoiseach at a private meeting that she did not think she could have proposals on the so-called backstop ready for next month, but was told time was running short.
Mrs May is working on new detailed proposals, but faces the difficult prospect of finding a solution that is palatable to the DUP - on whom she relies for a majority in Westminster - as well as to Europe and her own party.
Speaking at the conclusion of the summit, Mr Varadkar said all parties must be willing to make compromises, but would not be drawn on where there was room to move.
"I'm not going to make compromises here in the media. If I do have to make compromises in the future, they'll be made at the right point," he said.
"What we can't compromise on is those fundamentals. We need to make sure the common travel area is protected, that the rights of citizens in Northern Ireland are protected and that we have a legally operable backstop that assures us that a hard border won't emerge on the island of Ireland.
"But of course, language, detail, how you actually achieve those things - I think any reasonable person who wants to get an agreement has to be willing to compromise on those things."
Mrs May left the summit having been told that her Chequers blueprint was a non-runner, but EU leaders, including Mr Varadkar, said they could inform negotiations.
Asked about reports that Mrs May is willing to concede to some regulatory checks at Irish seaports, Mr Varadkar said: "I don't really want to comment on any of the detail of the proposals. We haven't seen anything in writing."
He said there had been a pattern of "verbal briefings, and being promised that certain things would happen, then, when the documents arrive, they are not quite what we expected".
"So the best thing I can do at this stage is not to comment on the detail of anything until I've seen it written down on black and white," Mr Varadkar said.
He also moved to reassure unionists in the North that it was not the objective of the EU to put a border between Northern Ireland and the rest of the UK.
Mr Varadkar rejected a suggestion that there was division among the 27 EU leaders, saying he had "never seen such unity".
It would be a "tactical error" to think otherwise he said.
He also rejected a suggestion from Hungarian prime minister Viktor Orban that some EU states wanted to punish the UK.