Europe does not want to impose a hard border on Ireland, a spokesman insisted on Wednesday, one day after he warned this would be inevitable after any "no deal" Brexit.

On Tuesday, EU Commission spokesman Margaritis Schinas had triggered concern in Dublin when he said the Irish border with Northern Ireland would have to be enforced.

If Britain leaves the European Union on March 29 without a withdrawal deal, the north-south border will become an external EU frontier, subject to customs controls.

The Irish government, however, insists it will not install "physical infrastructure" on a border that has been invisible since the Good Friday peace agreement.

EU officials say they stand in solidarity with Ireland, and that Britain must accept a divorce with a "backstop" to keep Northern Ireland in the same customs zone.

But Schinas' comment on Tuesday, confirming that if the British parliament rejects the backstop then the border will return, was seen as putting pressure on Dublin.

On Wednesday, he welcomed an opportunity at a news conference to rephrase his comments.

"The EU is determined to do all it can, deal or no deal, to avoid the need for a border and to protect peace in Northern Ireland," Schinas said.

"The EU is fully behind Ireland and we have expressed on numerous occasions full solidarity with Ireland. That has not changed," he continued.

"We will also continue to remind the government of the United Kingdom of its responsibilities under the Good Friday agreement, deal or no deal."

This was different in tone from what he had said a day earlier when asked about a no deal: "I think it is pretty obvious: you will have a hard border."

But the official did not fully withdraw this warning.

"At the same time Ireland and the EU have responsibilities as regards the protection of the single market and of the customs union," he said Wednesday.

"A product that enters Northern Ireland coming from another part of the United Kingdom enters the single market as a whole."