The UK and EU need to "knuckle down" and resolve the dispute over Northern Ireland's post-Brexit arrangements, the Irish premier has said.
Taoiseach Micheal Martin said he was encouraged progress was being made, and with the change in "mood music".
Brexit Minister Lord Frost will hold further talks with European Commission vice-president Maros Sefcovic on Friday.
What is the Northern Ireland Protocol and why are the EU and UK still fighting over sausages?
The UK is still warning it could unilaterally suspend parts of the Northern Ireland deal unless major changes are made.
In an interview with the BBC, Mr Martin cautioned the UK against triggering Article 16 of the Northern Ireland Protocol – which would suspend part of the arrangements.
The Northern Ireland Protocol prevents a hard border with Ireland by keeping Northern Ireland in the EU's single market, but that meant checks on products crossing the Irish Sea from Great Britain.
It states that Northern Ireland will remain part of the UK's customs territory however, it will have to stick to some EU rules to allow goods to move freely into te Republic and rest of the EU.
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Mr Martin said this would have a "very negative" impact.
He added the European Commission had put forward a "comprehensive package of measures" to address the concerns raised about the protocol, adding that some EU members thought Mr Sefcovic had gone "too far" in the concessions he had offered to reduce checks.
The Taoiseach said "I get on well with Boris Johnson on a personal level" when asked if he trusted the UK Prime Minister.
In Parliament, Lord Frost said Brussels should not interpret his "reasonable tone" in talks to imply any softening of the UK's position and Article 16 is still "very much on the table".
He told the House of Lords: "Whatever messages to the contrary the EU think they have heard or read, our position has not changed."
Lord Frost said an agreement is the best way forward but "I would not recommend any outcome from the negotiations that I did not believe safeguarded political, economic or social stability in Northern Ireland".
Meanwhile, Mr Martin will join ministers and leaders from across the UK and Ireland in Cardiff for a session of the British-Irish Council.