Ursula von der leyen, the european commission president, is to hold talks with boris johnson on saturday following an inconclusive round of trade negotiations in brussels.
The two sides will speak on the phone following the final scheduled round of future relationship talks, due to wrap up on friday afternoon, with time for a deal growing short and progress in the discussions still uneven.
Eu officials said brussels had received mixed messages from the uk this week, with progress in some areas such as eu access to british fishing waters but a continued lack of momentum on the critical issue of state aid.
Brussels has been puzzled by different signals from the uk, with officials in london briefing that they were optimistic about a breakthrough even as negotiators struggled to advance on some of the key sticking points.
London had hoped that talks would rapidly move into the so-called tunnel, or submarine status, under which the most senior negotiators would work in a small group to thrash out difficult issues with minimal outside scrutiny.
It will now fall to mr johnson, the uk prime minister, and ms von der leyen to chart a course, with entrance into the tunnel being one possibility although eu officials said this outcome was far from certain.
The call will take place against the backdrop of intensifying discussions between brussels and downing street. ms von der leyen has stressed in recent weeks her belief that a deal remains possible even if time is getting short.
Michel barnier, the eus brexit negotiator, will hold talks with german chancellor angela merkel on monday, brussels has confirmed.
Mr barnier met david frost, his uk counterpart, on friday morning to take stock of the weeks discussions in brussels. mr barnier has said the realistic deadline for any deal is october 31, given the need for the european parliament to review it before ratification.
Britains post-brexit transition period expires at the end of this year, meaning any deal needs to be fully in place ahead of that cliff-edge.
Mr barnier has identified four key areas where landing zones need to be found before a tunnel can be entered. these are so-called level playing field standards for business, particularly in the area of state subsidies; access to british waters for the eu fishing fleet; future co-operation on criminal justice; and governance of the future deal.
Eu officials spoke of a continued lack of momentum in the talks on subsidies during this weeks round.
Ms von der leyen is likely to press mr johnson particularly in the area of the level playing field, an issue on which the uk is internally divided. the conclusion of the latest round of talks comes a day after brussels sent a letter of formal notice to the uk over mr johnsons internal market bill which would override elements of last years uk withdrawal treaty in relation to northern ireland.
The letter is the first stage of a process that could lead to britain being hauled before the european court of justice. ms von der leyen will update eu leaders about the state of play on brexit at a summit in brussels on friday.
Michel martin, irelands prime minister, said he was looking forward to giving his assessment of the brexit situation to fellow eu leaders at the summit.
This included, he said the importance of protecting the adherence to the withdrawal agreement and the ireland protocol that had been agreed last year and the importance of european union solidarity in that context.
In addition, he stressed the importance of supporting the commissions negotiating team in relation to the negotiation of a sensible, sustainable long-term relationship agreement. that, he added, is important in terms of trade, protection of jobs and so forth.
Additional reporting by michael peel in brussels