The UK and European Union on Friday vowed to step up efforts to resolve a post-Brexit row over trade in Northern Ireland, after talks broke up without agreement.
The two sides have been at loggerheads over the rules governing trade in the British province, which London says is unworkable but Brussels maintains is needed to protect the integrity of the EU single market.
Prime Minister Boris Johnson's government is threatening to trigger a suspension clause in the deal, prompting the EU to warn of "serious consequences" if it goes ahead.
UK Brexit minister David Frost hosted European Commission vice-president Maros Sefcovic in London to try to break the stalemate, against accusations of political brinkmanship.
But Downing Street quoted Frost as saying there remained "significant gaps" between the two sides' positions, and suspending the so-called protocol was still on the table.
Talks had been "constructive", a government spokesman said, but "new energy and impetus" was needed in the talks to make headway.
"Accordingly, intensified talks will take place between teams in Brussels next week on all issues, giving particular attention to medicines and customs issues," he added.
"Lord Frost and the vice-president will meet at the end of the week to consider progress."
Sefcovic said separately that Brussels was prepared to look at "any issue" to reach agreement and the EU was "working around the clock" for a solution.
Negotiators would tackle customs issues and "focus like a laser beam next week on medicines", where drugs supplies to Northern Ireland have been caught up in regulatory red-tape.
But Brussels remained steadfast in its opposition to a UK demand to remove European judicial oversight on disputes with the protocol, he said.
"On the European court, on our side definitely nothing's changed," he told a news conference.
- 'Game of chicken' -
The thorny issue of Northern Ireland has bedevilled the entire Brexit process, ever since the UK's seismic vote to quit the EU in 2016.
The protocol, introduced when the UK finally left the European single market and customs union in January, imposes checks on goods heading to Northern Ireland from mainland Great Britain -- England, Wales and Scotland -- to prevent them travelling into the EU unchecked via member state Ireland.
An open border between Northern Ireland and Ireland was a key requirement of the 1998 peace deal which ended three decades of violence over British rule in the province.
But despite recent polling indications that a majority of people in Northern Ireland support the protocol, pro-UK unionist parties are unanimously opposed and there have been violent protests from hardliners.
They see the imposition of checks -- and keeping Northern Ireland subject to a raft of EU rules -- as threatening its position as part of the wider UK.
Removing the European Court of Justice is a red line for the EU but it has proposed reducing the number of required customs checks to ease logjams.
Frost said on Wednesday the talks could have several more weeks to run, calling for calm as talk mounted of Europe suspending the wider Brexit trade deal and slapping third-country trade tariffs on the UK.
Northern Ireland's biggest unionist party has called for the protocol to be scrapped, and threatened to collapse the power-sharing government in Belfast if it is kept.
DUP leader Jeffrey Donaldson said this week he backed Frost and that London was within its rights to consider suspension, which has seen Ireland meet to discuss contingencies if the talks break down.
But pro-Ireland nationalists warned the UK's stance was causing instability and uncertainty for people and businesses.
"We need solutions," said Sinn Fein leader Mary Lou McDonald on a visit to border county of Armagh. "What we don't need is ongoing brinkmanship.
"We do not need the British government, David Frost or anyone else, playing a game of chicken with the European institutions."