Brits have been warned they face two weeks in quarantine if they decide to go on holiday this summer.
Cabinet minister Brandon Lewis urged the public to reconsider plans to travel abroad, ahead of more formal guidelines due to be published this afternoon.
The Northern Ireland Secretary told BBC Breakfast: "The reality is, we are saying to people: if you are going abroad, you need to look at the fact you may well need to quarantine when you come back."
However, he stressed that the measures – due to come into force next month – will be be reviewed every three weeks.
Mr Lewis told the programme: “I can’t say how long this quarantine will last for, that is something that will be down to the scientific advice at every stage as we assess it in terms of keeping that R (infection) level down.”
Home Secretary Priti Patel is expected to outline the plans at Friday's daily Downing Street briefing, which will see travellers face potential spot checks and £1,000 fines if they fail to self-isolate for 14 days after arriving in the UK.
The Northern Ireland Secretary also poured cold water on hopes for so-called "air bridges" between the UK and lower-risk countries.
Under the proposals, backed by Transport Secretary Grant Shapps earlier this week, countries with infection rates of below one would be exempted from the quarantine restrictions.
However, Mr Lewis said in a separate interview with Sky News on Friday morning "there are no plans at the moment" to introduce air bridges.
He told the broadcaster that the Government needed to do what is right and "good for the health of the UK and our visitors".
But, offering a glimmer of hope, he added: "These things are always kept under review," meaning measures could change before July.
