EU and UK officials are to resume talks Monday on Britain's plans for a managed Brexit after a weekend hiatus during which London was under pressure to revise its proposals.
The European Commission is adamant that, as they stand, "the UK proposals do not provide a basis for concluding an agreement".
That grates with Britain's government, which considers the proposals it submitted on Wednesday to be "a fair and reasonable compromise".
After hours-long talks in Brussels on Friday failed to move the dial, a UK spokesman said: "We want a deal and talks continue on Monday on the basis of our offer."
Time is running short for the two sides to close the gap.
British Prime Minister Boris Johnson is determined to take his country out of the the European Union at the end of this month.
An October 17-18 EU summit is to determine whether Britain is headed for a Brexit deal, no-deal, or an extension.
- A week's window -
But European diplomats emphasise that London needs to offer revised, viable proposals within days and certainly before the end of next week, so any haggling and legalistic work is done before the summit.
"Everything must move very quickly and any negotiation has to start at the beginning of next week," one diplomat told AFP. "We will evaluate next Friday whether it's been possible to bring the positions closer."
Although Johnson has called his Brexit proposals a broad "landing zone" the EU's chief negotiator, Michel Barnier, and his team are unsure how far Britain will budge.
The EU refuses to characterise the talks held so far as negotiations, underlining a preference to stick with a Brexit withdrawal agreement that was struck with Johnson's predecessor Theresa May but rejected three times by British MPs.
- 'Backstop' headache -
The main sticking point is a "backstop" for Northern Ireland.
That is meant to guarantee no border springs up between the British territory and EU member Ireland, threatening a hard-won peace accord, while also maintaining the integrity of the EU's single market.
Britain's current idea for an alternative to the backstop -- which would see all the UK, or at least Northern Ireland, remaining in the EU's customs union -- is for untried technology to remove the need for most but not all border checks, and for EU standards on goods to continue to apply in Northern Ireland to facilitate trade.
The border plan is not acceptable for the EU. It sees the potential for rampant smuggling, especially as Johnson intends for the rest of the UK to diverge from EU labour, environmental and tax norms to aim for a regulation-lite economy on Europe's doorstep.
Nor does the EU agree with a proposal that Northern Ireland's assembly be given a right to effectively veto the post-Brexit customs arrangement.
If either of those two proposals are red lines for Johnson, it is hard to see the EU moving talks into the negotiation phase.
Yet if he bends on them, he risks losing tenuous support in the UK parliament to maybe pass a Brexit deal, reliant on 10 Democratic Unionist MPs from Northern Ireland and hard-core Brexit MPs in his Conservative Party.
- Extension option -
If thwarted, Johnson's best bet may lie with early elections.
There he also faces a challenge, with the UK parliament having passed a law requiring him to seek a Brexit extension from the EU by October 19 if he has not reached a deal by then.
British media speculated that Johnson might seek to sabotage any extension request he is forced to make against his will.
One path included his ministers asking an EU member state to block the unanimous approval needed for an extension, with Hungary cited as a likely ally to break EU ranks.
But Budapest denied Britain had approached it with such a request, and a Hungarian foreign ministry source told AFP: "To date there is no request for a delay, hence there is no point in speculating about anything."