The UK has called on the EU to be more pragmatic while the bloc in turn urged Britain to help rebuild trust as they prepare for talks this week regarding the Northern Ireland Protocol.
Since Brexit, EU-UK relations have soured with both sides accusing the other of acting in bad faith over the protocol which introduced checks on some goods moving from Britain to the North.
The checks have caused a perception among unionists in the North that the Brexit deal divides them from the rest of the UK.
"We ultimately need to re-establish a minimum level of trust that allows us to find solutions," Joao Vale de Almeida, the EU ambassador to Britain, told Times Radio before the talks which are expected to resume on Wednesday.
He added: "I remain confident that we can get there."
The envoy said no viable alternative to the protocol, designed to prevent a hard border between the North and the Republic, had been proposed, calling on the UK to honour its agreements.
David Frost, the UK's minister in charge of EU ties, said EU negotiators needed to adopt a "new playbook" for talks.
In comments published by the Financial Times, Frost said the EU needed to show more pragmatism and less "legal purism".
"We continue to work for negotiated solutions which achieve this. But time is starting to run out. We need to see progress soon. I hope we can this week," he said, adding the UK has made huge compromises to make the agreement work.
Earlier this year, UK prime minister Boris Johnson unilaterally extended a grace period on certain checks to minimise supply disruption, however, the EU said this move breached the Brexit divorce deal.