British Prime Minister Theresa May arrives at the Council of the European Union on the first day of the European Council leaders' summit on June 28, 2018 in Brussels, Belgium. Jack Taylor | Getty Images

Brexit will be the main topic of debate at a special summit of European leaders on Sunday and there are plenty of issues related to U.K.'s departure from the European Union (EU) that could be troubling those in attendance. The meeting of the European Council, made up of the EU's heads of state and government, will see the bloc's remaining 27 leaders meet to endorse (or not) a draft Brexit deal that was struck last week between Britain and EU negotiators. These are some of the issues about the proposed Brexit deal that are bothering some EU members and likely to dominate the summit.

Future relationships

Teams of negotiators from the U.K. and the EU have spent nearly the last two years reaching a draft deal on Brexit. They finally published last week a 585-page withdrawal agreement that covered a £39 billion divorce bill, citizens' rights post-Brexit and an agreement on the Irish border. But while that draft deal has had many detractors in London, and might not even be approved by the U.K. parliament, it's a separate, shorter 'Political Declaration' on the much-vaunted "future relationship" with Britain that's causing problems ahead of the summit. This had been due for publication Tuesday and was delayed because some member states are not happy with its wording. But on Thursday, Donald Tusk, the president of the European Council, said there had been "an agreement in principle" on the draft text outlining a future relationship and that this needed to be endorsed, at an EU-level, on Sunday. Tweet There future relationship concerns a wide variety of sectors including trade and security, fishing and financial services, to intellectual property rights, transport and energy. Details of the Political Declaration reported Thursday by Reuters said that both the U.K. and EU "envisage having a trading relationship on goods that is as close as possible, with a view to facilitating the ease of legitimate trade." It also said an economic partnership should ensure there are no tariffs, fees or quantitative restrictions across all sectors."

Tthe President of the European Commission Jean-Claude Juncker embraces the Prime Minister of the United Kingdom Theresa May on June 28, 2018 in Brussels, Belgium. Thierry Monasse | Getty Images News | Getty Images

The delay in the document's publication had troubled some top-ranking EU officials with media reports suggesting that German Chancellor Angela Merkel was ready to pull out of the summit unless the Political Declaration was finalized in good time before it begins. The thorny subjects of Gibraltar and post-Brexit fishing rights — issues always likely to rear their ugly heads at some point in the Brexit negotiation process — have already come to the fore as possible stumbling blocks.

Gibraltar

No sooner had the U.K. and EU promoted their hard-fought withdrawal agreement last week, than were Theresa May's political opponents in the U.K. lined up to knock it, vote against it, and even ready to oust the British prime minister. May has seemingly survived a coup for now, but the disgruntlement has spread to the continent, with several EU member states starting to request clarifications and assurances from the withdrawal agreement and the forthcoming political declaration on future ties. Spain has made the strongest statement so far, saying that it would vote against the draft Brexit deal on Sunday if changes were not made to the wording of the deal to ensure that it is included in any future talks on the status of Gibraltar, a British territory off Spain's southern coast.

May discussed the current state of Brexit negotiations with European Commission President Jean-Claude Juncker on Wednesday and then later phoned her counterpart in Spain. Downing Street signalled that May was open to negotiations, saying she had told Spanish Prime Minister Pedro Sanchez that the U.K. and Gibraltar "looked forward to these discussions (with Spain) continuing as we discuss the future relationship."

Fishing rights

One of the least sexy talking points of Brexit and the U.K.'s future relationship with Europe concerns fishing rights. Essentially, this surrounds access to fish in U.K. waters and is a big deal for both sides. The EU, in particular France, wants to ensure that European fishing fleets will retain access to U.K. waters after Brexit. Meanwhile, British fishing fleets are unsurprisingly pressuring London to "take back control" of U.K. waters. Downing Street's "outline" Political Declaration on a future relationship with the EU states that both sides will cooperate to ensure sustainable fishing levels and that they will establish "a new fisheries agreement on, inter alia (among other things), access to waters and quota shares" to be in place after a 21-month transition period following the U.K.'s withdrawal from the EU on March 29.

A picture shows a 'Fishing For Leave' campaign group sign about Brexit on a boat in the harbour in Brixham, southern England, on October 11, 2018. ROBIN MILLARD | AFP | Getty Images

There is fear on both sides of the English Channel, or La Manche as the French call it, that fishing rights will be used as a bargaining chip, or easily conceded, in any deal on a future relationship. Recently, scuffles broke out between British and French fisherman over scallop fishing, showing that feelings run high over fishing rights at sea, as well as in theory. Spain, Belgium, Denmark, Portugal and the Netherlands have all expressed concerns that the draft withdrawal agreement does not address fishing rights.

Level playing field