European Commission president Ursula von der Leyen, has said that crunch talks with UK prime minister Boris Johnson are stuck on three critical issues and "further effort" will be made to break the deadlock.
In a televised statement, following an hour-long discussion with Johnson, she said: "In a phone call today on the on-going negotiations between the EU and the UK, we welcomed the fact that progress has been achieved in many areas.
"Nevertheless, significant differences remain on three critical issues: level playing field, governance and fisheries. Both sides underlined that no agreement is feasible if these issues are not resolved.
"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.
"We are therefore instructing our chief negotiators to reconvene tomorrow in Brussels.”
The pair are due to commence talks on Monday evening with Brexit negotiators to hold talks on Sunday.
It comes after UK’s chief negotiator David Frost and his EU counterpart Michel Barnier announced on Friday they were putting discussions on "pause" to allow political leaders to take stock.
The pair said in a joint statement, following talks in London, that the conditions for a deal had still not been met, adding that "significant divergences" remained following a week of intensive talks.
“After one week of intense negotiations in London, the two chief negotiators agreed today that the conditions for an agreement are not met, due to significant divergences on level playing field, governance and fisheries,” Frost and Barnier said.
On Saturday, Barnier said "if there is still a way, we will see.”
The leaders were called in to break the impasse, but the clock is ticking on to get a deal through the door before the UK leaves EU trading rules on 31 December.
While both sides have agreed on most things, they have failed to solve their differences on key sticking points such as fishing rights, the rules governing state subsidies for business and how the agreement is policed.
Last week, Britain’s foreign secretary Dominic Raab has urged the European Union to accept a "point of principle" on fisheries — a key sticking point in reaching an agreement. The foreign secretary was positive and said that the country was in a “reasonable position” and there's a “deal to be done,” adding negotiations might soon be “reaching a conclusion.”
Watch: What is a no-deal Brexit and what are the potential consequences?