Boris Johnson and EU Commission president Ursula von der Leyen this evening failed to make a breakthrough in deadlocked Brexit trade talks and instructed the chief negotiators to meet again tomorrow. The announcement came after the Prime Minister and Ms von der Leyen held a crucial phone call as they sought to secure a deal ahead of Britain's departure from the EU next month. The Prime Minister and the the president of the European Commission said in a joint statement: "In a phone call today on the on-going negotiations between the European Union and the United Kingdom, 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. “We will speak again on Monday evening.” It came after the European Union's chief Brexit negotiator left London on Saturday and told reporters the two sides "would see" if a deal was still possible. Michel Barnier and Mr Johnson have been in crunch talks to try to strike a trade agreement, but Mr Barnier admitted there were still "significant divergences". Mr Barnier, who has been negotiating with the Prime Minister and his team for the last week, said as he departed his hotel in the capital: "We will keep calm as always and if there is still a way, we will see". The French politician said on Friday evening that despite "intense negotiations", conditions for an agreement had not been met due to "significant divergences on level playing field, governance and fisheries". It is thought the Prime Minister will resume discussions with Mr Barnier on Sunday. A spokesman for Mr Johnson said: "There are still some issues to overcome. Time is in very short supply and we are at a very difficult point in the talks. "What is certain is we will not be able agree a deal that doesn't respect our fundamental principles on sovereignty, fishing and control."