Johnson hopes a deal will be agreed in time for EU leaders to approve it at a summit in Brussels on Thursday and Friday. But he would still have to convince a deeply divided British parliament to ratify the agreement, probably at a rare Saturday session on October 19. If he succeeded, the world's fifth largest economy would split from its biggest trading partner with arrangements in place to minimise disruption at borders and preserve the complex supply chains that underpin the economy.
If he failed, lawmakers would begin a battle to delay Brexit that could end up being decided in the courts. Johnson has said he would do his utmost to pull Britain out on October 31, even without a deal - a move he believes would boost his hopes of political survival. "A lot of work remains to be done," the European Commission, the EU's executive, said in a statement on Sunday evening.
It said talks would continue on Monday and EU negotiator Michel Barnier would update the 27 member states - all except Britain - at a meeting in Luxembourg on Tuesday. "Differences persist on customs," said an EU diplomat. Underlining that there would be no technical Brexit negotiations at the summit itself, the diplomat said: "Small chances (remain) that a text could be ready for the summit and we won't negotiate at the summit. If talks are going well, we might say there is progress but more time is needed to continue."
A delay to the October 31 departure date could still be required even if a deal were agreed in the coming days, as time would still be needed to fine-tune the deal. "It's up to the Brits do decide if they will ask for an extension," European Commission head Jean-Claude Juncker said in an interview with Austrian media outlet Kurier. "But if Boris Johnson were to ask for extra time - which probably he won't - I would consider it unhistoric to refuse such a request."
Extension options range from as short as an extra month to half a year or longer and the other EU states would need to agree unanimously to grant it. If Britain leaves the EU without a deal, experts have said there could be serious short-term disruption with possible food, fuel and medicine shortages, and long-term damage to Britain's reputation as a stable home for foreign investment.