The Taoiseach has said that Brexit amounts to the most significant fundamental economic change the country has faced in 50 years.
Speaking at Dublin Port, Micheál Martin said he remains hopeful that a deal can be struck, adding it is in the best interests of Ireland, the UK and the European Union.
He warned that, even with a deal, the seamless trade that has existed up to now will not continue.
The Taoiseach urged small businesses, which either export to or import from the UK, to register and engage.
He said he was concerned there was some complacency in the small and medium-sized enterprises sector and he urged these firms to prepare.
Asked if he was confident that dispute mechanisms in any agreement would be effective, Mr Martin said building trust would be the key priority once a deal was struck.
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Earlier, the EU's Brexit negotiator said "fundamental differences" persisted in trade talks with Britain but that both sides were pushing hard for a deal.
"After technical discussions this weekend, negotiations continue online today ... Time is short. Fundamental divergences still remain, but we are continuing to work hard for a deal," said Michel Barnier.
On Friday, it is understood that member states were told that 95% of the text was complete but there were still big gaps on fisheries, the so-called level playing field, governance and how disputes will be solved.
There is concern that the process will not have enough time.
The transition period ends at 11pm on 31 December and any deal will have to go through a series of time-consuming legal procedures, including ratification by the European Parliament.
Additional reporting Reuters