The EU will “try everything” and “work to the point of exhaustion” to get the Brexit deal done, the European Commission president promised Boris Johnson after he called on Brussels to put “a tiger in the tank” of the trade negotiations. During Monday’s summit talks, Ursula von der Leyen said her negotiators would work until the last minute before midnight on December 31 and do everything possible to avoid the UK leaving the transition period without a trade agreement with the bloc. Speaking in French, the Prime Minister had earlier invoked Jacques Delors, the commission president when Mr Johnson was the Telegraph’s Brussels Correspondent in the early 1990s. Mr Delors once said his commission was the “tiger in the tank” of EU integration, borrowing an old slogan for Esso petrol. EU officials will be working through the summer holidays on Brexit and both sides have agreed an intensified schedule of talks in July and August. Failure to meet the deadline, which was definitively set on Friday when formal notice was given the UK would not ask for an extension to the transition period, would mean the UK and EU trading on WTO terms, which include tariffs. Mrs von der Leyen’s determination to avoid no deal is shared by her mentor Angela Merkel, the German Chancellor. Germany takes over the rotating presidency of the EU in July, which will hand Mrs Merkel an even more influential role in Brussels as the Brexit process enters its closing, crucial months. Mr Johnson, Mrs von der Leyen and the presidents of the European Council and Parliament, repeated their commitment to sealing the zero tariff, zero quota trade deal Her team, while appreciating the challenge ahead, is optimistic a deal can be done if both sides are prepared to compromise over the vexed issues of the level playing field, European Court of Justice and fishing rights. Mrs von der Leyen told Mr Johnson that there would need to be level playing field guarantees in the final trade deal otherwise it would never be agreed by the EU member states. She said that the level playing field guarantees on tax, state aid, labour rights and the environment would also protect Britain from unfair competition from EU businesses. Mr Johnson told her the UK had to be free to set its own laws after Brexit. The former German defence minister was adamant that the European Court of Justice would have to be involved if there was any question of interpreting EU law as part of the final agreement. She insisted that the EU would not drop its demand that the trade deal, fishing agreement and other aspects of the future relationship, be part of an overarching agreement underpinned by a single dispute settlement system. The UK wants any fishing agreement to be separate to the trade agreement and to prevent any situation where there is a single enforcement and punishment mechanism governing different agreements. Despite the divisions, the EU team remains committed to completing a fully-fledged, comprehensive trade agreement by October, which would allow time for the deal to be ratified by the European Parliament and member states. The Telegraph understands that, if forced, the EU could negotiate a more bare bones deal before the deadline and add to that basic agreement with more negotiations in the new year. Negotiators are expected to prioritise talks in the areas that would cause the most economic damage if no trade agreement was sealed by the deadline. David Frost and Michel Barnier, their chief negotiators, will now attempt to find new ways to engineer the necessary breakthroughs in the deadlocked talks. The two men are expected to discuss whether the best method would be for the sides to exchange non-papers, present legal papers or attempt another way of bridging the divides between the two sides.