EU and UK negotiators held "technical talks" in Brussels on Saturday with no sign of them breaking an impasse over post-Brexit fishing rights in time to save a trade deal.
Sources on both sides said fishing is now the main obstacle to any pact that could be in place on January 1 to prevent a sudden return to tariffs that would deal an economic jolt on both sides of the Channel.
"It remains very blocked," one EU diplomat told AFP.
One EU diplomat said Barnier had proposed EU fishermen giving up nearly a quarter of the value of the fish they catch in UK waters. Britain is understood to be holding out for getting back much more than half.
The UK has suggested this compromise last for three years before it is renegotiated, whereas Europe is holding out for seven. "It's all down to numbers now," the European diplomat said.
The EU's pointman in the talks, Michel Barnier, has consulted member states that share fishing waters with Britain on the haggling over the issue, the diplomat said.
The European Parliament has highlighted a deadline of midnight (2300 GMT) on Sunday as the last moment to receive a deal for review if MEPs are to ratify it before the end of the year under streamlined procedures.
Their UK parliamentary counterparts are in recess, but can be recalled within 48 hours to do likewise.
But EU capitals are not binding themselves to the European Parliament's deadline.
France's European affairs minister, Clement Beaune, warned that time left to get a deal was "a matter of hours," echoing words used by Barnier a day earlier.
But, he told French radio, talks will not be called to a halt even if they go past Sunday.
"We won't do that because what is at risk is whole sectors like fishing, like sustainable competition conditions for our businesses," he said.
- 'Concerns' Britain not ready -
The urgency of reaching a deal is being driven home by scenes of long lines of trucks at the entrance to the freight rail link that goes through the Channel tunnel as British companies frantically stockpile.
A group of UK MPs warned in a reported released Saturday that Britain has not yet installed all the complex IT systems and port infrastructure needed to ensure post-Brexit trade with the EU runs smoothly.
"With just seven working days until the end of the transition period, significant concerns remain," said Hilary Benn, a prominent Labour MP who chairs the cross-party Committee on the Future Relationship with the EU that put out the study.
Disruption is inevitable whether a deal happens or not. Outside the single market, British and European traders will have to fill out import-export, health and tax forms to send and receive goods.
A deal would lighten that burden by removing tariffs, but there would still be traffic snarls as checks on truck loads and drivers' papers are carried out.
Even small things, such as the truck drivers' lunches, will come under border scrutiny: the British government warned packed ham and cheese sandwiches are banned from entry into Europe under meat and dairy restrictions that apply to non-EU arrivals.
- Weighing up fish -
The European Union linked the fishing rights issue to the overall trade deal from the start. It is an economically tiny activity for both sides, but politically potent, able to galvanise media and voters.
Both sides have come down from their initial positions, with Britain accepting some EU boats will continue to ply its waters and EU countries recognising their catches there will have to be cut.
The haggling is over how much, for what species, in what waters exactly, and for how long a fishing agreement should last before it is put up for review.
The EU and Britain share stocks of 125 species of fish, some of which migrate across what will be the post-Brexit maritime boundaries, others which spawn in one part and swim in another.
Regardless of any trade deal, both sides are bound by the UN Convention on the Law of the Sea to jointly manage those stocks to prevent overfishing them to extinction.