Britain is "unlikely" to make the Republic of Ireland's list of countries exempt from quarantine rules, its Foreign Minister has said.
Simon Coveney also admitted there was "no question" the United States would not make the so-called "green list".
Mr Coveney said the list, due to be published on Monday, will not be particularly long.
It is likely to leave Northern Ireland and the Republic with very different exemption policies.
People arriving in Northern Ireland from 59 countries and 14 British overseas territories are no longer required to quarantine.
Currently people arriving in the Republic from overseas -with limited exceptions such as essential supply chain workers -are required to fill in a passenger locator form and self-quarantine for 14 days.
People crossing the border from here are not subject to restrictions on their movement.
Travellers arriving in the Republic from countries on the new green list will not be required to isolate for two weeks.
People can still enter the Republic from countries not on the green list, but they will be required to self-isolate.
Mr Coveney said Cabinet decisions on which countries would be included on the list will be based on science and epidemiological data and not politics.
He said countries will be excluded from the green list if their Covid-19 infection rates exceed a set threshold.
"I think there's no question that the US will be on the green list, it won't be," he told the Pat Kenny Show on Newstalk.
"And I think it's very unlikely our closest neighbour either will be under that threshold that we set.
"And that's really unfortunate because the two countries that we would like to be opening up to, in terms of international travel, are the UK and the US, given the integration between our economy of those two countries and of course the number of visitors that would like to come here to spend money in hotels and have holidays here and so on."