British and EU negotiators embark on probably their final two-day scramble to secure a post-Brexit trade deal Sunday, after failing to reach an agreement for eight months.
Michel Barnier and his UK counterpart David Frost will resume talks in Brussels where they broke off on Friday, calling a pause after a fruitless week of late-night wrangling in London.
"We will see if there is a way forward," Barnier tweeted.
Meanwhile, UK Prime Minister Boris Johnson will reportedly lobby European leaders, after a call with EU chief Ursula von der Leyen on Saturday ended with the sides still facing "significant differences" on the key issues.
The pair's next call will be on Monday evening and then the 27 EU leaders will gather in Brussels on Thursday for a two-day summit planned to tackle their own budget dispute, but which will now once again be clouded by Brexit worries.
Johnson and von der Leyen's issued a downbeat joint statement after their call.
"Whilst recognising the seriousness of these differences, we agreed that a further effort should be undertaken by our negotiating teams to assess whether they can be resolved," they said.
While much has been agreed, the sides cannot close out the thorniest debates over fishing rights, fair trade rules and an enforcement mechanism to govern any deal.
Britain formally left the EU in January, nearly four years after a referendum on membership that split the nation down the middle and two months after Johnson won an election touting what he claimed was an "oven-ready" Brexit deal.
The UK is bound to the EU's tariff-free single market until a post-Brexit transition period expires the end of the year -- an immovable deadline by which time the two sides must try to agree on the exact nature of their future relationship.
"Anything is possible. The three open issues are linked by Britain's intent to keep sovereignty a priority and Europe's fear of UK freeloading," a source with close knowledge of the talks told AFP.
Without a deal, the bulk of cross-Channel trade will revert to World Trade Organization terms, a return to tariffs and quotas after almost five decades of close economic and political integration.
Talks through this year have finalised most aspects of an agreement, with Britain set to leave the EU single market and customs union, but the three core issues are unresolved.
Johnson has insisted Britain will "prosper mightily" whatever the outcome of the talks, but he will face severe political and economic fallout if he cannot seal a deal.
"If we fail to get an agreement with the European Union, this will be a serious failure of statecraft," influential Conservative lawmaker Tom Tugendhat told the Lowy Institute in an interview published Saturday.
European capitals have remained remarkably united behind Barnier through the fraught Brexit process, but some internal fractures have now begun to surface.
On Friday, France threatened to veto any deal that falls short of their demands on ensuring fair trade and access to UK fishing waters, where they have demanded a durable agreement, whereas Britain wants frequent renegotiations.
"We know that 100 percent access to fishing waters in the UK maritime zone is finished," European Affairs minister Clement Beaune told le Journal du Dimanche.
"But we need lasting access. The British can't have total access to our EU single market and exclude fish."
Belgium, the Netherlands, Spain and Denmark share Paris's concerns that the EU side could give too much ground on rules to maintain competition.
There are just days left to finalise a deal, with an EU leaders' summit on Thursday looming large and the European Parliament repeatedly insisting that it needs time to evaluate and ratify any compromise.
Brussels, Belgium | AFP