THE EUROPEAN Commission has warned that the protocol remains the only way to prevent the return of a hard border in Ireland.
Thursday's late-night talks between the commission vice-president Maros Sefcovic and Brexit minister Lord Frost aimed at resolving differences over the implementation of the Irish Sea border broke up without an agreement.
In a statement, a British government spokesman said that while there had been "some positive momentum", a number of "difficult issues" remain to be resolved.
Both sides agreed there should be further "intensified contacts" in the coming weeks.
The protocol has been blamed as a factor behind the recent spate of disorder amid concerns among loyalists that it potentially weakens their place in the UK.
Under its terms - designed to prevent the return of a hard border - Northern Ireland remains in the EU single market for goods, meaning that products coming from the rest of the UK are subject to border controls.
Unionist politicians have been calling for it to be scrapped, but in a statement following the meeting, the commission insisted that it was the only way to maintain an open border with the Republic in line with the Good Friday Agreement.
"The vice-president reiterated the EU's commitment to the protocol, which is the only way to protect the Good Friday (Belfast) Agreement and to preserve peace and stability, while avoiding a hard border on the island of Ireland and maintaining the integrity of the EU single market," it said.
"Only joint solutions, agreed in the joint bodies established by the Withdrawal Agreement, can provide the stability and predictability that is needed in Northern Ireland."
It said the EU's legal action against the UK for unilaterally extending a series of "grace periods" in the protocol - intended to ease its implementation - would continue for "as long as necessary".
A British government spokesman said that in the talks, Lord Frost had reiterated the UK's commitment to working through the joint bodies provided for by the Brexit Withdrawal Agreement.
"He underlined that any solutions had to be consistent with the overriding commitment to respecting the Belfast (Good Friday) Agreement in all its dimensions and to ensuring minimum disruption of everyday lives in Northern Ireland," the spokesman said.
DUP deputy leader Nigel Dodds said the protocol was continuing to "wreak havoc on east-west trading relationships" and doing "real damage to the set of political agreements on Northern Ireland".
He said permanent solutions to what he termed "fundamental and far-reaching problems" were required quickly.
"It is clear from these remarks that the EU is simply focused on protecting its own interests rather than securing long-term answers which benefit communities and businesses across our province," he said.
"Maros Sefcovic believes solutions can only be found through full implementation and full compliance with the protocol – this belongs in the realm of fantasy, not political reality and negotiation."
Ulster Unionist leader Steve Aiken the statements issued after the Frost-Sefcovic meeting showed there was a "lack of urgency" in addressing the issues created by the protocol.
"Northern Ireland can`t afford to move at the snail`s pace of these negotiations," he said.
"The protocol is having a profound economic and societal impact in Northern Ireland on a daily basis and those issues need dealt with now."
