The Taoiseach has said he believes a Brexit trade deal will be struck and that Covid-19 makes it all the more crucial that another economic shock should be avoided.
Micheál Martin said his "gut instinct" is that British Prime Minister Boris Johnson wants a deal because he "gets the logic of it".
Speaking at a virtual meeting of the MacGill Summer School, Mr Martin said: "The momentum is towards a deal, towards an agreement.
"It will be very challenging but I think common sense should prevail all around.
"Given the enormity of the impact of Covid-19 on our societies, it would be very irresponsible of political leaders to visit a second shock on people."
The Taoiseach also insisted that there will be "no sealing of the border, and there will be no border on the island of Ireland as a result of this".
Mr Martin said while the British administration is "more volatile" than in previous eras, "I think the will is there".
He said he has "had words" with Mr Johnson about the Internal Market Bill, which he said got a more negative reaction from the British people than the prime minister might have expected.
Mr Martin said he believes the political will is there in the British Government to have a constructive relationship with the EU after Brexit.
"I think we can get a deal. I think the fact that the EU and the British Government are in intensive talks now is positive," he said.
"But it will be very challenging."
Mr Martin added: "Given the impact Covid-19 has had on our respective economies, logic and common sense would suggest that people need to do everything they possibly can to avoid a second shock to our respective economies and get a deal done."
Talks between the UK and EU on a post-Brexit trade deal are continuing through the weekend.
Negotiations resumed on Thursday after Mr Johnson last week called a temporary halt, accusing Brussels of refusing to compromise over the remaining differences.
Downing Street said the two sides, who are led by the EU's Michel Barnier and his UK counterpart David Frost, were now in "intensive talks", which would carry on through to Sunday.
Time is, however, running short if they are to get an agreement in place before the current Brexit transition period comes to an end at the end of the year.
Both the UK and the EU had previously said that they would need to get a deal by mid-October if it was to be implemented in time.
Mr Johnson has said that if there is no agreement, Britain will start trading with the bloc on "Australian terms", which is shorthand for World Trade Organisation rules.
However, the prospect of the imposition of tariffs and quotas has alarmed many British businesses already reeling from the fallout from the coronavirus pandemic.
The main obstacles to a deal remain fishing rights, so-called "level playing field" rules to ensure fair competition and the governance arrangements for any agreement.
Additional reporting PA
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