It should be "relatively easy" to maintain a soft border in Ireland as long as there is a zero-tariff trade deal with the EU, the Brexit secretary has said.
David Davis made the comment as he gave evidence to a House of Lords committee.
But he said that if there are tariffs on trade between the UK and the EU, then "we've got a real problem".
A zero-tariff deal alone would not necessarily be enough to eliminate the need for checks at the Irish border.
There would be a necessity for checks if the UK chooses to operate different product standards to those used by the EU.
There would also need to be some way to enforce rules of origin - checking that goods that are benefitting from zero tariffs come from the UK or EU.
Mr Davis said that the biggest non-tariff problem for the Irish border is food and agricultural safety standards.
He said the aim would be to get a "regulatory arrangement" to deal with that issue.
The EU imposes strict safety standards on food and agricultural imports, which involves checks at the point of entry.
Mr Davis said the UK had to "tread carefully" on the Irish border issue as the EU is "terribly suspicious" that it is being used to "lever an outcome" in the wider negotiations.
He added that the talks are at a point where Northern Ireland issues cannot be much advanced.
That is because the EU will not discuss trade until it deems "sufficient progress" has been made on separation issues, primarily the UK's financial obligations to the union.