Actually everything should be cleared by now. When EU leaders arrive in Brussels on Sunday, they just want to put their signatures under the two planned documents: the Great Britain Agreement and the Political Declaration on Future Relations.

But whether it happens, was on Friday even after the last meeting, the negotiators before the summit unclear. Almost all issues have been resolved, including the issue of access of EU fishing fleets to British waters. But one problem remained: Gibraltar. The Spanish government continues to insist on changes to the two agreements.

According to diplomats, the EU Commission, together with the Spanish and British governments, is working very hard to solve the problem. Time is running out: Several Member States, including Germany, have made it clear again on Friday that they are not ready for further negotiations on Sunday. The federal government has indirectly even threatened to let the summit burst otherwise.

Spain is bargaining for claims that are 300 years old

According to diplomats, several options were discussed on Friday evening. One is to adopt an additional paper on the territorial application of the Withdrawal Agreement, including Gibraltar, in addition to the Brexit Treaty and Political Declaration. How exactly it should be formulated, but is open - because London will hardly meet Spain's demands easily.

Spain has long been claiming Gibraltar, which has been under British rule since 1713. The Brexit agreement, the Madrid government fears, could lock Gibraltar's membership of the UK practically through the back door. She insists, therefore, that she has a right of veto on all agreements on the British overseas territory. British Prime Minister Theresa May emphasized that British rule over Gibraltar was "protected".

Spain head of government Pedro Sanchez tweeted after talks with May Thursday evening, "If there are no changes, we will veto the Brexit veto." Although Sanchez can not veto the withdrawal of Great Britain itself, as this could take place without an agreement if necessary. However, the Spaniard could definitely block the treaty, as the Council of the Head of State and Government decides by consensus in principle.

Spain isolated among member countries

That such an outrage is unlikely in Brussels, but not completely excluded. Spain is surprisingly stubborn, at the Sherpa meeting the representative of Madrid is said to have even thundered over the Treaty of Utrecht, which awarded Gibraltar to the British more than 300 years ago. However, understanding is limited in other EU countries.

"If the Spanish government ruptures the summit because of a non-problem, it has a problem," says an EU diplomat. In the circle of the member countries Spain was isolated with its procedure. EU Chief Negotiator Michel Barnier and Martin Selmayr, the powerful Secretary General of the EU Commission, are said to have expressed their incomprehension at the Sherpa meeting on Friday. The controversial article 184 in the exit agreement has been known for weeks and Spain has been fully involved, they say.

Insiders see a danger in the fact that the Spanish government has ventured too far on the Gibraltar issue - and now could face problems to return face-to-face. An upcoming regional election in Spain in December further complicates the situation. For some EU states, compassion is limited: how Sanchez gets out of this situation is his problem, writes a Brussels diplomat.

After all, Spain's Secretary of State for Europe Luis Marco Aguiriano already indicated a solution on Friday afternoon. They have a "promise" from the British government: "They are ready to guarantee that they agree with the clarification we want," Aguiriano said. However, he can not withdraw Spain's veto threat yet, since the British promise is not yet written.

Meanwhile, the federal government gives itself relaxed. Government spokesman Steffen Seibert: "We assume that until Sunday still open questions are resolved."