There has been a "change in tone" from the UK in the latest round of talks on the Northern Ireland Protocol, the EU has said.
Speaking at a news conference following discussions in London, European Commission vice-president Maros Sefcovic said: "I acknowledge and welcome the change in tone of discussion with David Frost today, and I hope this will lead to tangible results for the people in Northern Ireland."
Mr Sefcovic said the UK had to "reciprocate the big move the EU has made" on the protocol and stressed that "serious headway" needed to be made in talks next week.
Brussels, he said, was "working around the clock" to find a solution and both sides would "intensify" their discussions.
"We can and must arrive at the agreed solution that Northern Ireland truly deserves. That is also why I raised forcefully that we need to make serious headway in the course of next week," he said.
"This is particularly important as regards the issue of medicines. An uninterrupted long-term supply of medicines from Great Britain to Northern Ireland is the protocol-related issue on everyone's mind in Northern Ireland."
A UK government spokesperson said Lord Frost told Mr Sefcovic there "remained significant gaps to be bridged" between the two sides' positions.
It added that the pair will meet at the end of next week to "consider progress".
Providing a summary of the ground covered in Friday's talks, the spokesperson said: "He [Lord Frost] noted that, as set out to the House of Lords on 10 November, it remained the UK's preference to find a consensual way forward, but that Article 16 safeguards were a legitimate part of the protocol's provisions.
"Lord Frost also underlined the need to address the full range of issues the UK had identified in the course of discussions, if a comprehensive and durable solution was to be found that supported the Belfast (Good Friday) Agreement and was in the best interests of Northern Ireland.
"In this context, although talks had so far been conducted in a constructive spirit, Lord Frost underlined that in order to make progress, it was important to bring new energy and impetus to discussions."
The protocol is a key part of the Brexit withdrawal deal struck between London and Brussels and is designed to avoid a hard border on the island of Ireland.
As part of the arrangement, Northern Ireland remains under some EU rules and there are checks on goods entering Northern Ireland from Great Britain.
But having negotiated and signed up to the arrangement, the UK has now put forward proposals to change it.
The EU has responded with proposals that would cut checks on retail agri-food products arriving in Northern Ireland from Great Britain by 80%, along with a 50% reduction in customs paperwork.
But the role of the European Court of Justice (ECJ) in resolving disputes between the UK and the EU remains a key sticking point.